Leech is ridiculously OP. Not just that, but the fact that, without much planning, you can end up stacking resistances and stat effect immunities to the point where everything heals you instead of damaging you is pretty crazy.
By the end of the game my pyromancy battlemage with leech, lone wolf, stand your ground, full trait immunities and 100+ in all resistances was completely invulnerable. I would wildfire him, then battering ram solo into fights against a dozen enemies, cast explode/fireball/meteor strike and he would just stand there smashing people in the face with flurry and auto attacks as the world burned around him. Same with the final bossfight.
