Why the faction vendor weapons still aren't going to be that great
One word:
Mods
How many times do you pull a scavenger sniper mod? Where are the scavenger snipers? I have an Ego Precision Sniper, everytime I pull an ego precision mod it comes out being for a BMG. Where are the Ego precision BMGs? At 100 faction cost (which is equivalent to 1 weekly and 5 dailies-- so no less than 5 days between 7 days per 1 mod pull) how fast do you think you are going to be able to fully mod that new great faction weapon with matching synergy mods?
I believe FACTION vendor mods
are only found in the faction vendor random mod box. I'm not sure on this, but from what others have said it seems to be the case. The vendors that sell mods are only mods for NON faction synergies. The good thing about the faction weapons though is that they are higher damage. I'm not sure how much higher, but for instance the Frontier Saw from Top Notch Toolworks is a higher damage Saw than any other in the game. The synergies might be harder to come by, but those faction guns deal more dps than normal guns.