I think blockstun, although a nice challenge when you fight with a light weapon, isn't really needed as a balance mechanism as the game is already dominated by big, heavy, hard and long things. This is true even for 1h, as hammers have a much greater damage potential than stunnable swords. Also I completely agree WM does need more incentives. Blockstun is nowhere as critical an issue as hiltslashes though.
More importantly, I think something should be done about shieldstun. The heaviest weapons can stun shields on held strikes, but there's no visual indicator when this happens, which is a problem. This represent a serious issue with CT weapons as a held sideswing followed by an overhead is not avoidable if the sideswing stuns.