The resurrection mechanic bothers me not because it's a "new zombie feature" (a thoughtless idea borrowed by developers from other games), but because it simply doesn't suit the Heroes series. It's unnecessary. It never existed (or existed in heavily limited forms) in any of the Heroes games.
And the fact that healers have appeared only means one thing: healers should become the main target for fire-based magic. In other words, it changes the tactics of combat. Nothing more.
As for the unit designs, I'm ready to praise the developers (especially after the fifth game). When my hellish army clashes with a heavenly one on the battlefield, I experience a nerdgasm.