is it bug? if not what does it do
No, they are both aoe skills(sort of), corpse take goes like this
Step 1. Hit a group of enmies with Corpse take
Step 2. Kill said group of enemies
Step 3. Be healed
and corpse explosion works in a smilar fashion
Step 1. Target ONE enemy in a group of enemies and hit him with Corpse Explosion
Step 2. KILL the enemy you cast corpse explosion on
Step 3. all other enemies in the group are now hurt by a DoT
the DoT from corpse explosion is pretty weak IMO, i never used it after i tested it