Dark Seer + Witch Doctor

Why this works

Pulling enemies together with Vacuum can create a perfect setup for Witch Doctor. A multi-hero Maledict followed by Death Ward is a fight-winning combination on paper, and Dark Seer can even use Surge to help his ally position for the channel. The issue is that both heroes are committing their biggest spells to this one moment. If the enemy team is spread out or has saves ready for the Vacuum, the whole play can fall apart. This leaves both of them with long cooldowns and little to contribute until their spells are ready again.

Outside of that teamfight combo, Dark Seer and Witch Doctor don't offer each other much direct support. Their laning phases are usually separate, and their general game plans can diverge. Dark Seer wants to create sustained chaos with Ion Shell and his Wall of Replica, while Witch Doctor is focused on locking down and bursting targets. The success of the pair really hinges on landing that one big play. If they miss their window or the enemy anticipates the setup, they often feel like two heroes playing separate games until their ultimates are back online.