I've said this before, and I'll say it again, I dont think its a good idea to introduce a lv cap to get in the guild. (lv70s only, fine, but as far as a resilience cap goes, it should not be a must have to join).
If premades arent succeeding because of new players, with not so good gear, have a cap for premades, i have made a note in guild for premades to have at least 150 resilience. I think this is fair. Tho, if there are 20 people online, (15 of which have 250+ resil) and u are making a premade for AB / EotS, then you could get the higher resilience peeps to join.
This is ofc slightly unfair for the lower chaps, and i would expect some fair play, pls dont disclude them from the raid for the whole weekend, and include every1 u can with 150+ resil.
All this was worded better in my head, but i hope this gets the point accross