Is a -atk Brave Roy still Viable? And what skills do you recommend?

That's a huge shame that he's -atk, because it could sometimes mean, that his weapon passive won't trigger. You could try replacing his A skill with Swift sparrow if you have it, to keep his speed and add to his attack upon initiating, but it's kind of a rare skill (unless you are swimming in Brave Lyns).

Other than that, Fury should give him his lost attack and give him a permanent bonus to his other stats while also working well with desperation, so that's also a great option and probably even better than swift sparrow.