Based on a Cube Leeroy OTK Hunter i experimented few months ago (so i know this is not too bad in practice), the main problem it had was Leeroy being blocked by taunts, here taunts are not an issue anymore :)
5 Cards combo:
2x Play Dead
Execution of the combo:
1. Get all 5 combo pieces
2. Play Emperor Thaurissan and pass.
3. Play Clockwork Automaton (4 mana)
6. Hero power! (2 mana)
With 4 Clockwork Automaton on the board the 2 damage from the hero power being doubled 4 times (2 -> 4 -> 8 -> 16 -> 32), for a grand total of 32 damage.