I played the game with a party of 4 Rogues (+support spellcasters). With how the game handles flanking, at about level 9-11 (forgot when) they start doing 10+ (sneak) attacks per round each. Most encounters last only a few rounds, even bosses.
Not sure if it's the easiest way to play the game, but it certainly works for 99% of the enemies.
I assume turn-based probably makes this a bit harder, but not necessarily that much. Less attacks by you, but also less from enemies.