Hmm... so if I was a rusher as Assault and using the STG44 with iron sights it would be worth it, but if I were using the M1 Garand and being more standoffish than not so much.It depends on the scope. Up to 2x ADS speed is the same for Carbines, LMGs and Assault rifles (300ms), 3x bumps it up to 433ms. At that point the specialization is more valuable. SMGs have a lower base value (217ms) and are thus less effected by the percentage based (33%) perk. If you are fighting SMGs you're at a disadvantage with assault weapons and LMGs, less so with quick aim. Values may have been changed over time but that's how I remember them.
217ms quick aim -> gains 72ms advantage (over... other SMGs, and against pistols)
300ms quick aim -> gains 99ms advantage
433ms quick aim -> gains 143ms advantage