Whenever I saw some unnecessary requirements for an LFG group, I try to join. Last one was 318+ light level and above. We beat the entire raid first try for everything, even Oryx. Another first-try-for-everything run was only 315+ light, but everyone that joined ended up being 319. So although high light level and grimoire doesn't mean you are a great player and low light level and grimoire doesn't mean you're a terrible player, they account for some sort of skill. Dedication to the game? If you're 319+ light, you either got REALLY lucky or you've beaten several challenges. Most of which will be the challneges, since those lucky ones are in the minority now. As for gimoire, about 1000 of that is from ghosts, but I think it does account for your dedication. If you ended up collecting those ghosts, for me at least, it says that you've outplayed so much Destiny that you had more than enough free time to do these arbitrary tasks. Those that know Destiny in year one(and some year 2 people) understand the importance of small things in raids, and they usually have higher grimoire score and higher light levels. You can get a feel for whether a team will do well if they're laid back, if they talk often and they do things that aren't needed. If they're in the center at the beginning of the raid and shoot the doors, if the warpriest left side kills the right side acolytes that aren't in view for the right side, if people use supers on adds constantly to rotate supers around the entire time, if someone is done with their "jobs" for that quick 5 seconds of downtime and opt to help kill the other side's adds and stay active, if someone helps shoots all ogres in view when they can and/or kills the fourth light eater knight when they could have easily just run to center for safety and waited. It's the small things that can help you determine if you have a good team, because those small things can add up and make the raid go much more smoothly. It's also those small things that players learn through experience. They don't just learn the basic mechanics, they learn where adds spawn and the timing for everything. Every tiny aspect of the raid unfolds with every playthrough and when all players are at this same level, the raid becomes extremely easy. There are always exceptions, but these unnecessary requirements can sometimes actually yield good results.