Slardar + Tiny

Why this works

Facing a coordinated assault from these two is scary. A Blink-Crush from Slardar into an Avalanche-Toss from Tiny seems like guaranteed lockdown and burst on any single hero. The problem is they are both trying to do the same job. Tiny's combo provides so much magical damage that the target often dies before Slardar's Corrosive Haze can provide much value. Worse, a mistimed Toss can throw the enemy out of stun or melee range, completely breaking the chain of control and letting them escape what should have been an easy kill. Their initiations don't build on each other effectively.

This redundancy plays out in teamfights. Both Slardar and Tiny want to jump on a key target at the start of the fight. While they will almost certainly delete that hero, it means two major initiators have used all their spells on one person. This leaves the rest of the enemy team free to act, and the duo has very little left to offer for crowd control or peeling for their own backline. A smart opponent will bait this over-commitment, trading one of their heroes to leave the Slardar and Tiny exposed and out of position.