Fast shot gives flat +5 damage/attack (single or burst), wich is nice for spammers.
But for high luck bursters it's stupid to take it, because you can be very efficient with single shots in eyes.
LSW can turn into a midrange sniper rifle (same ammo,same ammo, same AP cost, -5 hexrange, almost same damage)
If you taged EW you will be able to use turboplasma rifle (awesome weapon)
If you taged SG you will be able to use 223 pistol
I have an avenger build, but I killed more ppl in PVP with 223 pistol.