I'm not entirely sure if the following is intended. I also do not know if it affects other maps as well:
Gankplank heals A LOT with Death's Dance when destroying barrels, even if they dont deal damage to anyone (just letting them explode somewhere). I think the tooltip says you heal for **damage dealt**. As he is not actually dealing damage with this barrels, i think he should not heal for it.
I hope someone can clarify and/or fix this.