Deep wounds is almost 50% weaker and is cancelled if your opponent hits 100% health. It's a considerably weaker dot than rend in every way. That said, I have no idea how hard prots abilities are hitting as I havent played a prot warrior in years. But Im not shocked that, in arena, they're able to out damage an affliction lock. They have pretty solid burst. I imagine they could be incredibly annoying in arena. But I saw a prot warrior in WSG last weekend and it was pretty laughable. But hey, maybe they were just worse than I am.