Xeviat
Hero
Exactly, GWM PM and SS are vastly superior to +2 in a stat unfortunately, I suppose that's why they made feats optional: They didn't bother balancing them.
Okay, so I went and crunched the numbers; when I initially looked at them, I completely forgot to include the -5 to hit for GWM ... how embarrassing.
So, lets assume the Barbarian only uses GWM with Rage and Reckless Attack:
No Rage, no GWM
Berserker deals 15.5 damage per round
Totem deals 14.35 damage per round (Polearm offhand) or 16.65 per round (if they get a cleave attack)
Rage, GWM +10 damage for Totem
Berserker deals 26.72, or 40.07 with Frenzy
Totem deals 33.90 with Polearm, or 36.33 with Cleave
The difference isn't too bad; it shows up the most when the Berserker isn't using Frenzy. Since Frenzy is only safely used 1/day, this could be an issue. As rage is 3/day (4/day?) at level 8, and combats are 3 rounds each, we get ... about 406.68 for the berserker and 434.25 for the feat using totemic barbarian.
But I think this shows that GWM's +10 damage is the source of the imbalance, not the berserker. The reason I say this is that their damage is nearly equal with Polearm or GWM's bonus attacks.