Slaughterer procs on all kills, it should only proc on melee kills.
DOT kills refresh slaughterer, and slaughterer augments DOT damage the interactions are all broken and janky.
I would also suggest that the buff ramp up slower but last longer.
5 seconds instead of 3.5. 5% power increase per kill. This is more in line with channeling our favourite gods will into the fray: Khorne. Whoops, edit: I mean da Emprah!