So got my flap Jack to 10 which gives this.
Passive ability -- smashing beak - damages a single target and has chance to stun the enemy.

Well I go to rooks nest solo and get to the boss. The boss couldn't move, I sat there and my bird kept him stunned 100%. Once I got to the two assassin spawns I literally had to desummon my bird so he could go to the portal and come back.

Now imagine a couple level 15 flap jacks, the level 15 passive must be even better, on an elite map.