I feel the Berserker is an ‘offensive’ specialization akin to Strength and Arms. Since the Warrior has some mandatory specializations (Tactics for dungeons, Discipline for everything) this means that the Berserker often competes for a spot with Strength. However, right now it feels like trading Strength for Berserker is a downgrade in damage, and Berserker isn’t nearly as useful as Strength is.
Strength:
1) is effective for both power and condition builds.
2) combines wonderfully with Tactics for support in dungeons/raids
3) offers cooldown reduction one of the warrior’s best weapons (greatsword)
4) makes the warrior much more powerful, even on its own
The Berserker simply can’t compare. Whether you want damage or support, you’re probably better of taking Strength – especially if you’re doing pve.
To help make Berserker more competitive, I think that the Berserker should grant might (or have a chance to grant might) on critical hits while in Berserk mode. This would give it a much-needed boost in damage, have more synergy with Tactics, make it a viable option in pve builds, and ultimately promote more build and weapon diversity (since you wouldn’t be tied to Strength and greatsword).