Dark Seer + Rubick

Why this works

Setting up a big Vacuum is the main idea here. Rubick can easily follow up on the clumped enemies with a Telekinesis lift, extending the disable. The problem is that after the initial setup, neither hero provides the necessary burst damage to secure kills. Dark Seer's contribution is mainly the setup and sustained damage from Ion Shell, while Rubick is also focused on control and utility. This leaves the duo feeling like half a combo, creating an opportunity that they themselves can't fully capitalize on. They need a heavy-hitting core right on top of the Vacuum to make it work, otherwise the moment is often wasted.

Across the game, this means their success is conditional. In lane, they can be annoying with Ion Shell and Fade Bolt, but they rarely have enough damage for a kill. In teamfights, everything hinges on what spells Rubick can find to steal and whether another ally is in position for the Vacuum. Dark Seer provides a very consistent setup, but he doesn't enable Rubick in any special way. Rubick is left to find his own impact from the enemy team's spell pool, making the overall performance of the pair unreliable from one game to the next.