Especially when I have teammates who I could entrust with certain tasks like Prime-Atlas-Shields.
I mostly play in PUGs however and I f******* hate shields at the moment.
This is a troublesome line of thought...
Call my cynical but I build all my characters to be able to handle themselves in a solo situation. If pugs happen to do something well, it's a bonus. Based on your weapon choice (which is a really good one), warp is the better option. Even though it doesn't get a bonus to shields, the Arc Pistol will make quick work of boss shields on it's own. You'll still be able to OHK most if not all mooks in a single charged shot, so things like bomber, marauder, centurian, nemesis, engineer, rocket trooper, hunter, and pyro shields are negligible. The question is, do you want to boost damage against 2 specific enemies (Atlas and Primes), or boost damage to basically everything else?
Personally I don't think Phasics have much use outside of high damage snipers (BW, Javelin, Widow, Mantis, Valient) and the Crusader and Executioner in order to ignore shield gate and OHK enemies. Any other time you want extra shield damage from ammo go with Disruptor so you can get tech bursts as well.