Since there might be some big ladder patches in the future, I just want to say my part about possible ways of making melee more balanced.
In general, there are many hero abilities that are never picked/useless that need to be buffed, such as firelord incinerate (rework as a strong counter to T1 mass rush?), farseer farsight (make farsight last 30 seconds?), alchemist chemical rage (could make it strong enough so people choose it as their first hero?), dark ranger drain life (allow it to heal allies/hero is immune to being interrupted when casting it?), bloodmage flamestrike (make it so the spell itself (not the animation) casts faster and so people cannot interrupt it by accidentally moving him, also make it use less mana so bloodmage incentivised as a first hero pick?), Keeper thorn aura (buff it so people actually choose it as a counter to melee rush?), cryptlord spiked carapace (strengthen it slightly or have it apply to beetles), blademaster mirror image (less mana needed, potentially images deal 5% damage of real hero so it is a real alternative to windwalk?), deathknight deathpact (allow it to give the DK a damage boost in addition to the heal temporarily?).
In terms of balancing heroes, there are ways to make certain heroes more viable as first pick, without ruining balance for them as third pick heroes. For example, take the paladin. A very common 3rd pick hero for human. Some might say that buffing him would not make him a first pick hero, as he would just be an even stronger 3rd pick hero. That depends on the way it is buffed. If you buffed all his abilities and made him have more hp/armour, then yes, he would stay as a 3rd pick, and simply become an even more guaranteed 3rd pick hero.
But if you were to buff his spells at later levels, like level 3, people might be incentivised to pick him 1st or 2nd, since those buffs would never normally be seen otherwise, as a 3rd pick hero would rarely hit level 5. His Str gain could also be altered, which woudl not be very visible at lower levels, but then at higher levels it would become very obvious. His damage slices could be increased so he deals far higher melee dps in general, which would not affect most games if he was picked as 3rd hero (because he only comes out late, so the total damage he would have done in game would not be much higher as he was hitting enemies less, and because 3rd pick heroes often die on the frontline since they dont have enough HP to survival fights/easily picked off).
These kinds of changes could make paladin a far better first pick, without buffing him as a 3rd pick. These are the kinds of changes we need. We need to see more variety of hero picks, even though it is not possible to make all heroes viable 1st picks as that would not really be possible.
In the future, hopefully we can see more early game bloodmage, paladin, dark ranger, tinker, beast master, firelord (not as a rush hero though, but as a legitimate pick). The key is to buff them in a way that does not make them stronger as 3rd picks (assuming they are even picked at all) through means of increasing physical DPS, stronger stat growth that becomes apparent later in the game and not early on (as a 3rd pick) and having some spells not increase incrementally but be very strong at level 3.
I would also hope to see more ultimate usage, since many heroes still don't bother to learn their lvl 6 spell if they ever get to that stage in the game.
As for non hero thoughts---
Batrider needs to have some legitimate reason to be made for a non-chemical explosion reason. Liquid fire could be made cheaper or he could be given more hp and damage. In order to avoid him being used to deal damage and then explode before death, his explosion damage could be tied to his current hit points.
Gargoyle buff, so that fiends do not replace him for one of his main roles as anti air (web could have a longer cooldown or require T3, stone form available at T2)
Glaive throwers/meat wagons/ catapults need more survivability (hp/armour). They were designed on basis of sieging bases, but in Wc3 almost all games are decided in skirmishes and not by sieging another base. They special upgrades (burning oil/glaive's splash upgrade) could be made cheaper.
Finally, Undead needs to be addressed. This race need a T2 melee unit. There is no way to get around this in my opinion. Some possible ideas are (far-fetched, I know, but there is no way to fix this race with small armour/hp changes) that necromancers (useless unit) can sacrifice themselves at the Sacrificial pit (also useless) which allows them to become permanent zombies.
Or, make the abomination weaker and unlockable at T2, and make the Frosty Wyrm a melee unit (like those dragonspawn creeps). This would also solve the issue of UD having 2 tier3 flying magic units, which is a serious problem.
The strength of the deathknight/lich really needs to be addressed too.
Finally, UD needs some kind of 2nd dispel, since the other races have 2 types of "dispel" type abilities. It could be related to using the corpses the meat wagons have collected for example (this concept could also be used for sa heal over time that is dispel-able, to make the DK not so crucial to the UD army).