Drow Ranger + Sniper

Why this works

Stacking slows from the backline gives this duo a way to control teamfights, assuming they have space. Drow Ranger's Frost Arrows can hold a target in place long enough for Sniper to line up his own shots and a clean Assassinate. If an enemy does try to close the gap, a well-timed Gust can knock them back and create the distance both heroes need to survive and keep attacking. They both want to do the exact same thing—hit from as far away as possible—and Drow’s kit offers some tools to help make that happen for the both of them.

The problem is that having both Drow Ranger and Sniper on one team creates a huge, obvious weakness. Enemies know they can win by simply diving the backline and bursting these two fragile heroes. This makes your draft very demanding; you absolutely need a durable frontline and good counter-initiation to protect them. The entire game becomes about whether your team can successfully peel for its two glass cannons, or if the enemy team can get on top of them. The outcome rarely feels decided by the synergy itself, but by how the other eight heroes play around it.