Dragon Polymorph useless ???
I find that skill great ! Since some of the flying enemies are really dangerous, I put at least 2 points into Polymorph !
In that case you can first Polymorph the most deadly opponent(s) and then concentrate on Towers... If that's done, back to the flying enemies ... polymorph again if needed and taarget lock on 1 polymorphed enemy and kill him with what you like most
Summon Friend is ONLY most useful (I find that) when you upgrade that skill to 5/5 !