the invoker healing should be base on magic power and not % on hp. but for dps your missing the point the invoker do hight dps on single or 4 monster max with basic attack the other class do medium damage on a large zone. the tank dragood class is one of them that do many aoe damage quicky on a large zone. the big problem of the game is it too easy and any class can play solo.
the game dificulty is unbalance not the class power
still unfair they outdamage a sentinel when they offer zero utility