Weapons, gear, and armor builds (Intellect, discipline, strength). If you inspect someone and they have 400 strength etc and nothing else, non leveled weapons or simply not a smart choice of weapons for said activity (trying to kill oracles with a Hawkmoon for example), and grimoire to a certain point. I have friends that have between 2500 and 2800 grimoire that have hundreds of raid completions, so as long as they're in the high 2000s give or take they're probably decent. Low 2000s or below you'll probably have to explain the encounter (even though they'll tell you they know what to do as they die over and over again)