Even without damage mod - which the OP says nothing about - your GWFS damage at level 1 goes from 11.33 to 19.66, where a TWF has 13. Now there is 0 reason to TWF, even at low levels, if you are a fighter.
Polearm Mastery bonus attack will deal 7.5 at max level, which is still less than 8.33.
As umpteen threads have shown, there's a problem with the fighter.
The extra ASI is massive, in terms of power. Feats are (or can be) very potent, and getting to max your attack stat by level 6 instead of 8 contributes a lot. Second Wind can be a nice way to stay in the fight. Maneuvers and extra crits, plus the extra ASI('s), really make up for plenty in terms of differences between the other classes.
Only one version of the fighter gets extra crits, and the number of extra crits is trivial. Also the fighter only gets extra ASIs at 6th and 14th level. So you have to wait until 6th level before you're statistically better than other PCs, and then wait until 14th level - by which time many games have ended - to get even better. The fighter needs an ability to counter the surge issue.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.