For those Psychologicals the best way to beat the game on heroic is shock therapy and traumatize (max) high voltage (filler) max charged blood and electrical storm at the same time until you can use wraith form after that max tenacity. Electrical storm recovers focus with no cost. the bar should be wraith form 2 traumatizes 2 electrical storms and 3 shock therapys.
For level 7 you can do this for 8 and 9 too. After you spent awhile at killing the enemies and you upgraded everything get your mana to 9999. Then fill up all your mana. Spam your highest unit as in for humans and orcs the highest melee unit. For elves highest ranged unit which could be the phantom archer their version of wizard or their version of paladin (haven't tried that that out yet so not sure.)
Theirs pretty much two plays to beat the game the fun way which most of us do.... and the cheap way for the fun way pick any character i don't really care who and go to the holy cross 8 star area easiest to beat get the dark shooters and start other areas or go alone *more fun* and for the cheap way whisper me and i'll tell you but its pretty boring