MMH5.5 - Heroes of Might and Magic 5.5

I'm not saying to remove this skill (not at all). But it deviates significantly from the concept of small, passive +2 bonuses, providing a very noticeable boost (effectively an essential skill that people take for Offense and tolerate the insignificant +5% bonuses).
If you compare Battle Frenzy to Aura of Swiftness, they are roughly equal in strength.
Vitality is noticeably weaker than Battle Frenzy, but it's still an order of magnitude stronger than the +2 bonuses.

If spells of level 4-5 are expensive, it means that with 40 knowledge, I can use Meteor Shower and Implosion every turn, while a hero with 10-15 knowledge will quickly run out of mana and have to switch to less powerful spells.
I suggested a concept of 5-10-20-40-80 mana (with an increase in the power of level 4-5 spells as well). With 10-15 knowledge, you won't be able to cast many spells that cost 40-80 mana (with Empowered, it will be 80-120, for a single use).
To make sure you understand correctly, this is not about weakening heroes with average knowledge (because the more expensive spells will be more powerful), but about unlocking the potential for mana scaling, unlocking super-spells for those heroes who have enough mana.
For example, a Fireball for 20 mana can work just as well as the current Meteor Shower for ~20 (if you increase the damage), and Meteor Shower and Shock can be made more expensive, to 40 and 80, while simultaneously significantly increasing the power of these spells.

6 months with 2 cities is a very, very large army (and 30-40 levels is also a lot). It's no wonder that your Magic heroes suffer, and you have to weaken the skills of Might heroes because of them.
For comparison, in a similar PvP RTA, the gains are from week 6 of 1 castle (!). And the hero levels are around 20, and the maximum SP ranges up to 30.
You have 10 times more troops, and SP is far from 200-300.

I just thought that you were aiming for 3-6 months, not about 6 months (not that long). About 6 months means 4-8 months of gameplay, not 3-6.

It's impossible, but 20-30 is quite possible (for a Warlock with skilled education). I have no doubt about this because, in the original game, I have seen level 20 heroes on week 3, since players who play effectively will not wait a long time to reach a high level if they can do it faster. Unless, of course, you have slowed down the experience gain from killing neutrals.
I repeat, for a complete balance test, you need players who are focused on playing quickly, as quickly and efficiently as possible, and not just people who like to play leisurely for 6 months. Try to attract someone among the active TE players.

For my part, I recently prefer pure PvP, and this is one of the reasons why I could not be the kind of player who would show you in practice what fast gameplay is like (I haven't played the original game in PvE for a long time). That is, it is difficult to get me involved in PvE; for this, a truly very cool and well-thought-out balance is needed to make it interesting. And in my understanding, a cool balance and weak skills are incompatible concepts, no matter what you write about accumulating small bonuses for a Might hero of level 30 :).
For example, if there are 30% offense or 30% archery and other comparable passive bonuses, I will say, "it sounds cool, I want to try it; in the original or other modifications, there are no such good skills, but you have." This feeling is comparable to a racer who likes speed but is limited by moving at a low speed only because he is overtaking a pedestrian, for whom the balance is built.
You will never have this feeling of rapid progress due to strong passive skills until Magic heroes suffer and are not able to deal enough damage with spells in a prolonged game (and for this, it is necessary to increase the cost and power of higher-level spells). Because when Magic heroes have enough mana, knowledge ceases to be valuable, and in fact, the Magic hero must fight on bare SP against two parameters: At, Df, and a growing army of Might.

You write about fast encounters on week 6; this means either the players are not playing fast enough, or you have some special map features or fundamental changes that do not allow you to meet on weeks 3-4, about which I do not yet know.

There is a map called Half-Random Tactical Arena; you can take it as a basis and rework the scripts for specific skills, and then you will have a ready-made arena for MMH5.5.

I would like to understand why you consider levels 30-40 attractive for PvP?