I see a couple issues that I have an idea to resolve...

1) Not many people get Side-by-Side. One of the reasons is that it's most useful when OTHER people also get Side-by-Side. So thus it's a chicken or the egg problem.

2) Warriors often avoid group-hunting because they prefer to beserk, and that doesn't play nicely with groups.

Solution! Give Warriors the inherent ability of Side-by-Side. Thus others may be more likely to get side-by-side, knowing at least all warriors have it, and warriors may be more apt to forgo the AS bonuses of berserk knowing they're getting bonuses from being in a group.

Though the engagement system near came, the protect/guard verbs and something like this at least makes it feel like warriors are good to have on the team for their physical combat knowledge, ya know?