I've been a titan from day 1, I have 1 of each class but both will always have a fraction of play time compared to my titan. I have never been discredited in a raid thankfully, maybe because I'm a lvl 30 and everyone wants that? I do know during atheon without a titan flash bang in the ports it's twice as hard for the relic holder, and if you have any chance of defeating atheon with less than 4 level 30's on hard you need weapons of light. For these reasons I run the raid multiple times a week with my titan to help out friends who need us, never been in a raid that was successful without at least 1 titan. I'm sure it's happened but not often.