Gyrocopter + Lina

Why this works

Picking these two together looks like a plan to delete heroes with overwhelming burst damage, but the reality is they often step on each other's toes. Both Gyrocopter and Lina typically want to be cores that farm quickly and hit a major power spike in the mid-game. When they're on the same team, they end up competing for the same resources. Their abilities also lack a clean setup for one another; Light Strike Array has a cast delay and Call Down is a slow, not a hard lockdown, making it difficult to guarantee that their combined damage will land on a key target before it can react.

This tension plays out from the very start of the game, as laning becomes awkward trying to find enough farm for both of them. Later on, teamfights become a problem because both heroes are fragile and want to be the main damage dealer. If the enemy team can survive their initial salvo of spells, neither Gyrocopter nor Lina has a good escape or the durability to survive a counter-attack. A team with both of them is all-in on ending the game early with damage, and if that plan fails, they have very few tools to fall back on.