This might help: http://samanna.net/eq.general/tiers.shtml
Sounds to me like you lack direction and are sort of haphazardly hopping about expansions in search of targets that you can kill and drop upgrades. Try to re-focus your guild on two objectives.
First objective is guild level gear improvement, which can be challenging for part time raid guilds. Your core raiding force is likely well geared to handle the content you're in, your focus for gear improvement should be continued farming of targets until your weakest members are keeping up with your core raiders. Choose a number of targets you can farm and stick with them until stuff is rotting or going to bots/alts. If your weak members fall to far behind, they become a liability as you push for your second objective. It sounds like CoA is your best bang for your buck farm zone right now. You should be hitting it once a week like clockwork. Shyra, all 3 DoN dragons and all three Relic dragons (all are approximately the same difficulty) should be on this list too. Hammer these till the lowest members are wearing the best gear they can offer. Don't sweat your core on these raids, they will get taken care of as you work your second objective.
Second is progression. Select an expansion and focus your efforts on keying and the progression that it offers. Don't hop around and dillute your efforts. Each expansion has a magical place I call "candyland" at the end. When you get there, you get big upgrades for your time investment. If you're already farming CoA, then DoD is your next logical choice. Start taking a stab at Vule to learn the event. Schedule 3 attempts a week on one of the blood raids until you have the strat and just pound on it till you win a couple times. Keep your curses cleared and just learn the events. Once you have all 5 beaten, work out a schedule and knock them all down keeping your curses. Don't mess with PoR until you're farming T1 of Demi. As you improve your guild level gear these events will become easier and easier.
IF, you're working both of these objectives, you'll be attracting new membership too. People who are going places attract others. Your partial raid attendance problem will likely sort itself out if you're making progress.