In my humble opinion the Rogue Idol works very well in a Big Waaagh list.
With the Wardokk's Ritual Dance (3+ add 1 to save) and Kunnin' Beast Spirit magic (add 1 to save) he can save at 2+/6+. Then you can buff him with the Warchanter to make him a very powerful killing machine.
Ardboyz as well, in the Big Waaagh find their natural habitat. They are useful to increase Waaagh Points and they are a very solid batteline saving at 4+/6+/6+, then hitting and wounding at 2/2 with rend 1! Buffed with a Warchanter make them one of the strongest unit in the game.
So of course, you idea of Rogue Idol + lots of Ardboyz is a very good idea to win matches and to be hated by your friends 😛