Witch Doctor is a great Support hero that has useful disable that can, with the right circumstances, result in a very long duration stun. He also has good utility in his heal, and good damage potential with Maledict and his Death Ward. You have to play him quite carefully though, as his armor and hp gain are quite low, so make sure to use your heal often in the early game to stay alive.
For mid to late game, aim to be in teamfights to throw cask,use your heal and do as much damage as possible with ult!
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