AstralLein
1) It's not out of the question that war machines will be brought back in the future. Not all mechanics are in the game from the start of early access. Neither the machines, nor water, nor the underground were deliberately removed. They've been postponed for the future so that the rest can be sorted out first.
2) Oh, those poor mages... the meta in the game is warrior-focused, and Avatar was overpowered for 1.5 patches, after which it fell into the gutter and is rarely played nowadays. Heroes has always had a fierce imbalance between schools of magic; in HoMM3 it was exacerbated by the walk mechanic, which inflated the usefulness of Earth and Air even further. In OE they made a separate walk system (HoMM5 did the same, except they also nerfed the spells themselves and removed some), and also initially wove it into the template mechanics. So walk is no longer some kind of imba for casters of specific schools, but an integral part of tempo. Also, OE doesn't have universally accessible mass slow, haste, and domination, for which the developers deserve a huge thank you.
3) Like mages, ranged units in OE are a suffering class. Why? It would take a long time to explain... there are many ways to counter them. Even excessively many.
4) The idea is that the hero defines the player's gameplay. That's why each faction has many imba heroes. More than there are bans. And again, mages currently lose to warriors in the meta. Even school specialists. Unfortunately, there are heroes with outright useless or too mediocre specializations, and this problem hasn't been addressed yet.
5) It came from the uselessness of the Capitol in HoMM3. No one among pros ever built it. OE has plenty of templates for building up with a large number of towns, and even there, tempo support is impossible without resource banks. The economy is balanced by the conditions of a specific template. Exodus, for example, gives you up to six towns and many resource banks over the course of the game. But somehow no one tries to squeeze in all seven tiers... can't afford it. Seems the economy isn't so all-powerful after all.
6) Same as in HoMM3 when taking meta land... The level there, by the way, wasn't needed.
7) The main purpose of dust is to upgrade artifacts and spells. And you don't get to bathe in it often.
8) Hive presses unit buttons the least, because of eggs. But it doesn't have that many abilities either. Everyone else presses them very often. Temple's self-buffs, all of Grove's awakenings and abilities (especially Grove), Necropolis ghosts rarely press, but coffins, liches, and dogs press constantly; Dungeon mostly uses stances, but medusa escape, dragon fire shield, assassin ranged strike, and minotaur attack ignore are also in demand. All situational. Neutrals usually have useful abilities too.
9) Temple is just unlucky with its racial ability in life. It'll probably be changed again soon. But HoMM5 also had solutions like the sworn enemy or overly expensive minicons for mages. And runes and blood rage were from DLC and were complete imba. Necromancy, by the way, was reworked in HoMM5. Gating nerfed? It's never been as imba as it is in OE. Those larvae are terrifyingly effective, and together with T6 worms they form the strongest Hive tactic.