I like the grim as an identifier as well, but as you know, it doesn't always reflect skill. I don't really care to judge guardians preemptively unless we're doing a high level activity, and I only do the judging internally. If its something I can carry them through Ill spend the time teaching what to do and how to get the guns and gear they need to be better. What I don't like is when I'm invited or join a group going into VoG hard/Crota hard or 34-35 PoE and the person doesn't have reasonable weapons, gear or light level and doesn't know strategy's. The higher tier activities should be something you attempt when the lower ones have been mastered. No matter what, I think the best way to tell is to play with the guardian and decide for yourself based off a real time display of skill or lack there of. I agree with the Ninja below, good company trumps my caring every time. My 2 best friends that I play with regularly have offensively low grim, lack a lot of the weapons, dont have very good tactics and cant adapt. But we're laughing the entire time and having fun so I usually dont pay attention to how often Im reviving them or having to wipe because of them.