It looks like as a tempest fighter you'll have the same to hit bonus as either Sword&Board or Great Weapon fighters, provided you use 'offhand' weapons (such as the shortsword). Damage wise, you're looking at +1 with non 'offhand' weapons, so you're effectively power-attacking by losing the to-hit bonus, or far better, +2 with 'offhand' weapons, which brings your best damage shortsword or handaxe up to 1d6+2, which has a nice minimum, average as good as 1d10 but maximum as a longsword. Since you're attacking twice at-will, you'll never deal the devastating criticals that a GW fighter might, but you might hit twice for comparable damage since you don't get your strength modifier.
AC-wise, you are very flexible. Stick with chainmail and it'll be like you're in scale thanks to your feat. Go for scale and you'll have plate AC but in exchange for your damage bonus. So you can emulate the S&B fighter with a light shield, but not do better, or you can have slightly less AC than a plated GW fighter with a slightly higher damage output (I think, depending on your chance to hit). They run the whole spectrum and that's pretty cool.