About astral dmg, there are allot of units with that type, but also items/spells/medal with astral resistance so it evens out i a way.
I vote to leave phoenix pure fire dmg, and chaos dragon to change 50-50% fire/astral. Just my thought.
Nice work with gizmo improvement. Your changes in gizmo in KB-tL HoMM babies mod were great. Maybe lower heal/resurrect amount but add bonus res when hit ally units. It already act as fit of energy spell for +1 action, so would it be possible to add low lvl divine armor for 1 turn or something ?
Ah, same as HoMM babies, no more 100+ turn battle with mana/rage inflow
As for upgrading companions look for Trigger and his improvement for ranged units crit%, or Elenhel counter for wanderer spell scrols. It`s nice idea to get better bonuses from companion after 10/20/30/40 battle something like wives in KB-tL, and more reason to keep him with you, instead just kick him on the curb when better comes along