305 is fine for everything up to Oryx at which point you will be promptly ground into a fine powder.
Obviously higher is better but I've had a couple 305 folks in runs up to then, as long as the overall team is strong.
Hey Drizzay, have you seen the Defender Titan w/ Blessing of Light + Touch of Malice strategy for the Ogres?
A Defender is the floater who pops a Blessing bubble in the middle and then uses the Touch of Malice to make quick work of the Orges as he/she can dip back into the bubble to regain an overshield, which the Touch of Malice uses first instead of health.
Seems like a great way to increase DPS during that phase.