If Bitcoin was just a payment method (which it's not, but I'll get on to that in a second) it would probably go to multiple department heads (finance, legal, customer services) I suspect.

We're talking however of Blizzard taking payments in an unproven, highly volatile currency with limited ability to guarantee they can get their money back out again, or use the currency in any straight forward manner (e.g. to pay staff). Yes, that would probably go to the board if a case could be made for it, and it's difficult to see the advantage to them at this point.