Sniper + Viper

Why this works

Stacking slows from two different cores seems like it should control the game, but the opposite often happens. The problem is that both heroes offer a similar solution—damage from a distance—without covering each other's weaknesses. Viper needs a target locked down by stuns so he can apply his corrosive damage over time, and Sniper needs hard disables on anyone who jumps on him. Neither hero provides that critical lockdown for the other. Instead, you end up with two stationary damage dealers who are vulnerable to the exact same type of coordinated dive, as their slows don't prevent enemies from blinking in.

In practice, this puts enormous pressure on the other three players to draft entirely around saving two immobile cores. Both Sniper and Viper need farm to be effective, and they often function best in the same mid lane, which can create tension from the start. Later on, if the enemy team can get past the initial slow from a Viper Strike or Shrapnel field, there is little follow-up control to protect the backline. The lineup lacks a natural initiator, making your game plan predictable and easy to fracture with aggressive plays.