Right, that is exactly why I suggest adding more levels for those towers. Then, the new max lvl arrow, bomb, etc. towers would be more relevant.
And already now the maximum level for different tower types is different, so it wouldn’t break any “rule” to differ the maximum levels a bit further.
And about the healer: Lots of questions there!
What do you all think, should he just increase the current hitpoints of injured troops/hero, or also heal from poison/fire like the heal spell? Area of effect or single target? Continuous heal or “healing shot” every X seconds? Should healers be able to heal themselves?
Also, how would a healer unit behave apart from the actual healing part, i.e. when no injured units are close by? Should they stay near other units and wait for them to get injured, or rather move forward alone? What should healers do to the hostile castle gate or hero tent when they don’t actually deal any damage at all? I mean, even mortars and mummies, both ignoring all towers, can at least attack the castle gate…
I guess the correct balancing of healers as part of the defensive waves would be quite complicated: At a chokepoint, one or two healers could keep the other units dealing suppressing fire to the raiding party alive for much longer and (if they can remove poison and fire effects) make certain units much less effective, while e.g. arblasters (high instant damage) would be as efficient as before, shifting the balance of other units quite drastically.
Also, should those healers be able to heal troops and hero only, or also towers, hero tents and castle gates? I mean, the heal spell can heal the hero tent, too, and basically a tower is more similar to a tent or a cannon than to a living soldier.