I have a f2P account where I used him a lot. Being a early game account where I have no champion pool he is very good, and is on every single team for me including CB. He brings decrease defense, poisons, and his passive as well as the skill that ignores block damage/unkillable makes him very good for arena.
I would say he could be good for sand devil's but i dont think you would be able to make use of his sleep good enough.
Really just depends on champion roster, I have a large roster on my main account and would really have no use for him, wouldn't mind one but would never get around to building him.
I think he is a really cool champion and probably best used in arenas. Most end game account would probably have little use for him though.