here i'll in first tell you which first ability should be add (for free) and the other one must be upgrade, then if someone focus in one unit it'll be sometimes better.
The first matter is with the towers : i'll explain this.
-When i played your map for now a lot of times i found that mixe grounded-tanked units with tower because towers can't be killed, unliked range units that are slaughed by ennemies heroes and theirs spells. Orc towers are useless, they don't do real damage and have nothing special so their cost is just too expensive and it's just a waste, about 15 damage is nothing in late game, even in the beginning it's almost nothing. In all of the humain tower i looked and out of that :
-Guard towers are useless, damage less than average, even with the upgrade they aren't a real support for killing ennemy.
-Multishoot tower look good but doesn't do enough damage too (even if i didn't tried it so much).
-Glaive tower are just...null, they have a weak range with a average speed and even if they bounce the damage isn't enough strong.
-Acarne Tower : the fire tower gave me really a bad impression, 70-80 damage but average speed and their speed don't match for killing a mass of units with heroes, the lightning tower bounce but it's just slow and damageless, a full fire canon tower max upgaded deal easily 4 or 5 time the same damage in zone, same with water that can't help... (i think it'll be better if tower had spells like lightning chain or somehing like that)
-On the top of that is the cannon tower, really something that don't let the tower idea fell on the deeps inutility. Canon tower don't look strong at first but are really good when you upgrade them, the matter with cannon tower is that units could run out of the range of the cannontower-shoot that'where units come, a few elvens giants can block units and canons tower can easily fire with their 1000 range, the initial attackspeed of canon tower is really slow but you can increase it by a lot (70% if i am right) in the woodcutting building just by upgrading them. The usual technique that i use is on the center massing tower and then make 2 ice tower on the extrem left and right side for slowing attack and move of ennemy and making all other tower in fire cannon tower. At the end you have easily more than 1000 DPS in the two sides in AoE damage (without armor tough).
However cannons towers are good they aren't imba, they are just nice balanced, you can't win with them but it's almost impossible to win without them. (in hard mode and harder with 2 heros)
1-Units Amelioration
#1 : Add abilities to units
Humain Race
Milita, footman and Knight : have a high cost for no really a good deal, i think you should add Drunken Brawler with 20%x2 and 10 or 7% chance to dodge for both milita and footman and add something like that to the knight (with lower critical but more dodge because they are riding)+ "Charge" : A bash spell with 10-20% chance to do some damage with 1 sec stun for unit and no stun for heros (or it'll be too imba).
Also you could add
"Honor of the Knight", a reincarnation spell with 1 second delay and 180 cd, won't unbalanced the game since units are build for free but'll look nice with the ressurection effet and'll help a bit.
Sharpshooter : Also add some Drunken brawler (i think every unit should have one, more or less good, especially for human), you can just add a critical strike with low chance but high damage for a "markanship" effet like 5-7.5% chance to do 5 times normal damage.
for additionnal skil
"Explosive Shoot" using the Annihlation Orb of the UD destructor for create a strong shoot with cooldown, no mana need but only cd because if we use mana we could regen it with priest or fountain and it'll become imba. (turn on automatic) however if you use the "fire arrows" could be better, the one thing sure is that you shouldn't give "Orb of Annihlation" both to Sharpshooter and Tank (as i propose later)
Elven Priest : Healer they need something, i think using "retablissement" of UD'll be better than the actual 2 aura healing because if i am right the retablissement is an aura which heal both heal and mana, anyway increase a bit the regen (to 30-35 hp) and reduce the mana regain to 5 (10'll be kinda too much).
In additional Skill i think you should add Roar instand of interior fire with name of "
Light of Hope" because make some priest manually boost unit is a shame when you have no time.
Sorceress : Just unneeded, their slow spell affect heros for only a few seconds and her other 2 spells aren't good enough to help that.
I think that instead of sorceress you should add Spellbreaker unit.
If you really want the sorceress then make her attack decrease armor instead of "lucioles" because we can't use more than one automatic spell at the same time and increase the duration of "slow" but make the cd of "slow". In additionnal spell...well... it's hard but i propose a fusion (like with hypogriff) with another unit for make a special type of unit but it'll be hard to find a good idea.
Flying Machine : A uneeded unit because this unit is too weak, mechanical (can't be boost by shaman) also the number of damage is too low and the number of unit created by building is low.
I think you should better remove this unit because of this weakness and because if we mass this unit it may cause lag.
Mortar : Well not really extremtly good it deal quite damage but tower are way stronger so i think this unit could be removed and have to be removed or completly changed.
Tank : Changing the damage and make give it flamme attack was not a bad idea however the tank is just too weak comparing of his price, plus it's mechanical so we can't buff him with furie of shaman (well you could make furie able to target mechanical). I have a good idea for tank.
-Give Him the "Fire of Phoenix" With a rocket graphic and long Cd it'would be funny to see rocket from tank, automatically firing. The other possibility if you want is the "Orb of Annihlation" from the destructor UD as i proposed before for a AOE damage.
-If you accept trigger skill then instead you can give "Rockets" Spell to the tank and use a trigger for using it automatically.
If you accept this possibility then the better way is to give "Orb of Annihlation" instead "fire of phoenix" without mana cost and adjust the cd to every 4/5 shoot of the tank, the rocket then should be fire every 1 or 2 min with strong area-damage.
-If you don't change the spell of shaman as it's affect mechanical then add "spell immunity".
Griffon Rider: SInce it's also a human unit you should give "Drunken Brawler" to the griffon rider with 30-35% chance to deal 1.5-2 times normal damage and 25-30% chance to dodge. Also increase the aoe of the attack and his attack speed a very little bit more. A additional skill (very hard to find) a bash skill because they use hammer for attack, no stun hero but stun unit for 2-3 seconds however no deal damage (the stun no the attack).
Night Elves Race
Chasseresse : A unbalanced unit, she has quite fast attack, the bouncing is good but her attack is too low so she isn't enough strong.
I'll Continous later...
System Improvement
A funny big name for speak about upgrade. i think upgrade should be changed, the chasseresse is an example, she could have been good if we could upgrade her more so i propose :
-A team upgrading, instead of everyone doing their own upgrade, when someone buy the upgrade then the entire team is upgraded (could be very nice for team work).
-Alternatly 3 possiblity :
1st- Make every unit upgrade for everything, damage/armor/additional abilities etc...
2th- Use simply a race upgrade, probably the easier way to do this even if it give less possiblity on gameplay than every unit upgrade.
3th- Give an upgrade per type of unit. Exemple : Headtroll hunter and sharpshooter are both range unit so make upgrade affect these two.
Out of the tree possiblity i would recommand the 1st cause it's the best for gameplay, however it's the hardest to do, i guess if you don't have time the 2th is the better.
(Attackspeed and movespeed could be improved with a 5000 endurance range for unit only of course)
e13 Review :
Ninja : Incredible, a nice model and a hero really a bit too strong.
you've done a good hero however the skill that give X% to create an illusion and go invisible behind the attack is way too imba.
For balance it you should do 3 thing :
-reduce the chance of making an image because when there is too much creeps it's become insane, down chance lvl 6 to 28% chance maximum. (then increase agi damage to 4x agi (include bonus))
-Remove invisibity after create the illusion because when you are attacked you become invisible and stop attack... because of the chance of creating an illusion it's imba cause creeps never attack you more time than 3 or 4 times.
Also you should REALLY increase the overall damage of normal attack of heros because both range and melee heros do everything with spells and nothing with attack. The fault of that is firstly the attack speed of hero, i think all hero should have attack slightly increased + more base damage or more damage per principal abilities points... even with full upgrade str/agi/damage and armor your hero don't really do something himself without spell and melee become half useless.
Also items should REALLY be lot strong, when i see a item +3 agi or even +6 int i would never buy it or if it's dropped (like spider ring) i'll just sold it. I think that items should have more abilities and give more interesting thing because they are really useless until now.
I think adding a lot of items stronger and with special abilities would be good, just add some and add them to the market then player'll really have a look at them.
Also we really need one way to gain some gold because when we play full house we have always nearly no gold/wood and then we can't do anything...
About the spellbreaker i tried him only for a little bit but... he doesn't have spell who deal damage (or what you could call real damage), his drain skill is uneeded...
However about the firemage two things :
-The Fire pillar should deal 1.5 x more damage because it's strange that a spell lvl 5 who should deal 180 damage/sec for 3 second need help to kill a 540 hp skelleton. I think you should reduce the time between damage by 2 for damage every 0.5 and drop a bit the damage for that damage are equal to 1.5 what the spell should deal as it's now.
And i've got an idea for the ultimate of the firemage, it's using rain of Chaos of Archimonde who normally call mass infernal in different way. Originally this idea has been used in Hero Line Wars but it could be really good in this map. It's using the damage and stunning of the impact when infernal fall on the ground, if you change the damage cause by it and change infernal to dummy unit + reduce duration of unit to 0.01 then only the fall of the unit will cause damage and unit'll be removed, it's really incredible sometimes ! in addition you can vary the aoe for both fall of unit (so the aoe-damage around where unit fall) and the aoe of the spell itself for choose where units could fall, with the number of summoned of unit. Note that the times between 2 unit to fall is determined by the "Stats - Duration -Normal" and the stunning time is determined in inferno spell by the "Stats - Duration -Hero/Normal" and duration of the unit (by default infernal) by "Data - Duration".
Well i hope you'll be enough strong and a bit fool to read all that i wrotte (xd) and good luke for the mapmaking and everything else !