The first step is always to make it work consistently.Polishing details like individual weapons / weapon types - that takes a lot more time to design and balance.
Rifles are still "good" at stealth. Their silencers are just a lot less effective so that pistol/smg are arguably the best gun for stealth.
A compound bow does a little more damage than a pistol with HP... with AP steel arrows... and obviously it's another notch stealthier.
Crossbows are still murderous so no big change there. =)
Does that make a pistol a bad choice? With a 20 round magazine and potentially on full auto? Not even close.
Was it possible to play stealthy before? Absolutely. The agility-based weapons just didn't have the damage numbers to make this properly OP.
And yes, specialising in one attribute should be OP. Just ask someone going all in with fortitude. =)