I'm not sure how you utilize him, but if you're blitzing with him a lot and want to build him into a killer, then frenzy is a good choice. But you would lose some degree of control over him. Then, if you want more of a support and road block type then stand firm is good. Break tackle to to make him more mobile, although that's only +1 improvement to dodges over ag3 and since you can't decide whether to use it or not, it's not as good skill as on TT. Two heads would be superior to break tackle.
MA or AV don't seem like that hot picks to me. He already has high MA and AV is not a very proactive pick. Plus it's totally negated by claw.
So... basically what 20phoenix said ;) I think I'd pick stand firm.