My personal opinion is that he reminds he a lot of Nidoqueen and Lanturn. He may very well become a decent Pokemon in the lower tiers, due to some very handy resistances and interesting options. In OU, he could be used as a "niche pokemon", serving a very specific purpose in a metagame suited to his presence, despite average stats, thanks to intersting and unique typing. In other words, think of Nidoqueen, "Damn! My stall team still needs reliable toxic spikes, stealth rock, and a counter to Tyranitar or Lucario! Well..." I think that's basically what Warubiaru is going to be like.
That said, exactly what this set would look like, I don't know. Scarf seems like the best idea, functioning pretty similarly to Scarftar but with better typing (it seems). Overconfidence seems intriguing, and with perhaps Bulk Up I could see some offensive options- however, this would probably be in the lower tiers. I think that Scarf will be his most common set in OU- below that, things like Bulk Up, or even CB, as he definitely has the awesome STAB for that sort of thing. A very interesting Pokemon, to be sure.