Umbreon would be pretty much the best choice, as you guessed. A cursing set would be best for this, since curse lowers speed, and you have a speed lowering nature.
Umbreon @ Leftovers
252 HP Evs 252 SpD Evs 4 Def Evs
A healing tank, Curses up and rapes face. Wish for recovery, curse for added Defence, as well as Attack. Straight forward.