I've completed this map twice now (dwarf and tauren), and I have some things to say, especially since it seems you are making a sequel.
For starters, bless you for QWER hotkey setup instead of "intuitive" binds. And bless you even more for cinematic skip option, that was huge for replay enjoyment.
Now let's talk hero abilities. They're not very creative, but I suppose they don't have to be just because they can be. I'm undecided about having so many passives when you only have one hero to control.
The spellbooks were a nice addition. Even though autocast for Bloodlust/Inner Fire doesn't work on the hero, but he sure is happy to buff the treant, and even though I'm too inept to figure out how to change inventory hotkeys, I liked the spellbooks. I put combat and nature to good use. By the way, is it not possible to QWER these as well?
I didn't try to play a caster yet (for long anyway), because I was worried the spells would become too weak lategame since there's no gear scaling for casters in WC3, not without triggers anyway. However even on the end bosses, my dwarf/tauren spells took off a chunk of health so you balanced that somewhat. I say somewhat because eventually my barbarian could just attack move his way through most content, after he got his class belt and Gigas loot anyway. Have my doubts the mage will clear as easily even if I control her.
Before we leave the abilities topic, I'd like to point out that the mage intro doesn't mention her Mirror Image ability and the dwarf's Riposte made me think he would sometimes counterattack when struck in melee but in reality it just seems a differently tuned Bash.
Inventory. While the teleporting stash and obelisk storage space are useful, it still gets annoying to shuffle items around to get quest items and crafting reagents to the right place. I would prefer that these don't use up inventory space. Perhaps the spellbooks could be "learned" as well (only one active at a time), replacing the Patrol button on the command card. Patrol is just a poor man's bot program anyway, and there's little reason to patrol when nothing respawns. And I'd have a nicer hotkey than something on the NumPad. ;p
Regenerative consumables could work over a shorter duration. There's really nothing to do while waiting. Explore, oh whoops monsters, and they hit you and break the regen.
Now the roleplaying value. You make an acceptable adventurer, perhaps a bit too quick to accept your role in a prophecy and for some reason feeling great loyalty to the local king. But no cringy moments, a little humor here and there, a little nuance to the character. I can tell English is not your first language but your use of it is more than good enough for it to not bother me.
I'm not sure the obelisks were part of your initial plan but there are some mechanics that seem to pretend they don't exist. You mustn't leave this area until you've killed X. You may enter this special place, but we're locking the door behind you, so you just hope you find a way out. In all of these cases I can just teleport out. And back in.
Too many trash mobs seem to have their default WC3 names, which feels a bit lazy. Could have done a bit more to create a sense of your own universe here. The eredar could be called something else than eredar, and you wouldn't need to put any explanation anywhere to the new name, but I'd still come to associate it with demons.
And now in my random order of feedback let's talk more about monsters. Sadly there seems to be little work behind the AI as I can just run away from nearly any fight and regen faster than the mobs. Not the last one, thankfully. I can split up packs. I can kill one of the last bosses of the big dungeon and run away and regenerate before I take on the rest. This is fine with kobolds and trolls, but with Anubis and the guardians and whatnot, I think there should be a door that locks behind you at least. After expanding the rooms so that it's not hopeless to kite inside them.
Gigas stands out as an exception. Sure, he leashes like all the others but he certainly was a unique encounter that took some thinking. And this brings me to the secrets. I found the hidden heroes on my first playthrough, woop. I got my treant buddy, I got the armor set, and stuff and stuff and stuff.
But I didn't get past the riddle door on either playthrough. And, this thread hasn't really helped. You don't want spoilers posted here but you'll PM the answer to anyone who asks? This seems needlessly complicated to me. The door is, according to your own common issues, a bit bugged. So not only am I throwing guesses at it, I'm also hoping I'm standing on the right pixel while I'm doing it. And this has me here, asking, hoping for your or someone else's benevolence.
At some point however (perhaps this point), there won't be a response to a request like this, even though you're clearly happy to share it as long as it's in a PM. So now I'm asking you to simply post it. Put in a spoiler within a spoiler within a spoiler within a spoiler within a spoiler within a spoiler if you like, but post it. I am impressed with your work and I look forward to the sequel, but this particular part is just frustrating.