When people post for high levels when doing the raid, they are not necessarily interested in the level but the experience that comes with being such a high level. Before the update I was 319 on all characters. Only the lack of a 320 class item prevented me from being 320. I think I have done kings fall over 70 times. And it's almost impossible not to be a high level when completing the raid that many times. If a guardian at 309 joins your raid group chances are he won't understand the mechanics to the full. Because if he had completed it many times, then his light level would naturally be higher. I'm all for helping newbies through the raid, but there are occasions when time is of the essence, and you need to get through it quickly. So maybe this is why people ask for 320 + since the person will have completed the raid many times. And since everyone is experienced, a death here or there doesn't mean a wipe as everyone will know how to adapt.