Mighty blow
guard
standfirm
piling on - I think too good right now, but more because of how it interacts with MB and claw.
Idea for piling on- instead of hurting player, have its function be to try to prevent a player from getting up. So if you knock down a player somebody with piling on would try to pin that person on the ground to prevent them from getting back in the play.
ok skills
strong arm- I think it really should be in the passing category. I realize it says strong in it but it is a passing skill. Having it in passing would help 3 agility passing teams not have to rely on as much luck to develop a passer.
multi block- fun skill, not taken very often though.
break tackle- Fixed. I like it as it is. I should change my mind though just to fight with galak though

Juggernaut- I only really ever seen it taken on big guys, but it is not a bad skill overall. I don't really have any thoughts on how to improve it, or even if it needs improving.
bad skills
Grab- My suggestion to upgrade it. If you have grab and block somebody you get the effect of tentacles on that player until the start of your next turn. That way you could have a better chance of locking down a player in the open field.
thickskull- needs some serious love imo. I have only seen a thrall take the skill. It is not a bad skill to start on a player but it is not taken from what I have seen as a skill choice.