Phoenix + Venomancer

Why this works

The main issue here is doubling down on the same kind of damage. Both Phoenix and Venomancer excel at blanketing fights with magical damage over time, which sounds good until the enemy team buys a single Pipe of Insight and negates a huge part of your team’s entire game plan. There's also a serious lack of reliable stuns. Venomancer can't lock targets in place for a good Supernova, and Phoenix can't guarantee enemies stick around to soak up a full Poison Nova. Their kits don't enable each other; they simply add more of the same effect.

In practice, this means your big teamfight moments often fall flat. You might get a great start with Poison Nova hitting several heroes as Phoenix dives for Supernova, but opponents can frequently activate a Black King Bar or a team defensive item and simply walk out of danger. This leaves both your heroes with their ultimates on cooldown for minimal impact. The lineup lacks the control needed to force enemies to take the damage, making your primary win condition very fragile against teams who itemize correctly.