Just want to add that there is no rule that Infiltrators have to do anything. As long as you work together as a team, it doesn't matter much. I've played games where I was blocked from reaching an objective, having to help out a hard-pressed teammate or whatever, while someone else made it there so it didn't matter. Also, when not playing infiltrator, I rush for objectives all the same and never get it that others don't especially on hacking assignments. Sometimes someone is outside of the hacking area, getting killed repeatedly, needing to be revived, again, repeatedly. How does that help? Isn't working together a much better strategy?
Also, I had a Silver game yesterday that illustrated that it's not that easy. I went off, cloaked, to find the objective. As it turns out, my three remaining squadmembers then proceeded to get themselves killed. I tried to double back and revive them, as I stood no chance against two Geth Primes and assorted other baddies, still midway the mission, but kept getting shot, sometimes even when cloaked, while my teammates couldn't make it to cover or support each other and kept bleeding out. Yeah, that sucked and we didn't make it past that wave as I ran out of medigels... Sometimes the team just gets caught in a wave of baddies, what takes priority then? Going solo on Bronze may work, but on Silver or Gold?
I really wonder what is better, especially in a Silver or Gold match: move to the objective together as a team, or have the rest of the team stay put and try not to die while an infiltrator tries to do the objectives on his/her own, hoping that the cloak doesn't fail at the most inopportune time.