Harmony - Troop Symmetry

So, my answer is no; even +4.0 is probably not enough to make the special ability look relatively good.

Then let's consider a +5.0 bonus:
1) We've already discussed combat stats, and if +4.0 still looks weak, let's make it +5.0;
2) Now let's look at magic stats – giving an initial +5 bonus to knowledge... and goodbye to mana problems – doesn't that seem a bit excessive? And considering that the hero already has 1 and 2 knowledge at the start, we'll get 60-70 mana at the beginning of the game – in my opinion, this is even more powerful than Sinishtar's "Catalyst" special ability (the mana shortage issue is not solved by lowering the price, but by increasing the total amount).
At the same time, a +5 bonus to spellcasting doesn't seem overpowered (by the way, Chaos is generally weakened, and its damage is more like Chaos from Heroes 4).

Added 2 minutes later

I also think the explanation about the bonus to spellcasting and knowledge is very good.

Describe it briefly.