I typically only roll with one QB if he's good enough, (Brees/Rodgers/Peyton) I am rolling with Luck this season and have Wilson as my backup but yeah, what Kearly said makes sense, I always pickup the guys with the highest upside or are unknown so Bridgewater and maybe Bortles.
Orton or Alex Smith might be decent adds if you are desperate to have another QB but I like to let it ride with one unless someone really good is sitting on waivers or my starter gets hurt.
I dropped Brady last season and avoided him this year, he was terrible in regards to fantasy.
Funny note, I had Brees last year, picked up and played Foles on Brees bye week when Foles got injured and had a terrible game, dropped Foles only to see him out score most other QB's the rest of the year but in keeping only one QB, I was able to pick up tons of depth everywhere else to win out. That extra roster spot is valuable, QB's outside of the top 3 or so are a wash really.