Basically what Pinski said, there's not much more you can do, though you're on the right track with items. Due to the recent proc changes, most items were actually nerfed as far as their overall power return, but there are some still worth wearing.
What exactly are you raiding that there's so many problems?
In any case, here's an exhausted list of everything I can think of for your situation:
#1, mythical epic helps immensely with power management. It will probably solve all your power management problems...
#2, Dispersion: as noted it only helps when you're getting hit, but try it out. You can only get one proc at a time and this includes the power part - in fact you only gain the power when your get hit a second time, meaning you really have to be getting smacked if you want it to go off often. Only really helps against a massive AE mob.
#3, Manawell gear: in the meantime, ask your healers to wear one or two pieces of manawell gear. If they are still having problems, and can afford to swap out their items, and if you still kill contested Mayong, his leather hat is still an option. I would not advise the TLC belt or the older Di'zok / Chardok blue shiny belt, which used to be staples of the raid, due to the proc changes. A manawell item, or several items, can return 2000 or more power per minute. (Your buffs alone return, on average, 4000 power per minute).
#4, Tinker power: tell em to become tinkers so they at least have an emergency manastone?
#5, Mana cloak, if there's ae fights you can use it and it'll hit everyone's power back. but it's still not very much.
#6, Cannibalize thoughts: it's only returning about 200-300 power per cast, and you can only usually cast it once a minute, enough for your group to cast another spell. Better than nothing though.
#7, Power roots. Expensive as hell nowadays, but still good for emergencies.. look em the recipe to feed to plants at
eq2traders. You can have 1 root per tier, if you know what you're doing. They're no trade so you have to get your healers to buy em and use em, and they have a huge casting time. Power signets, power pots, manastone, bottled breath, Pantrilla tablet, Everliving stein are the other clicky items that exist to increase power, and basically listed in order of how easy it is to get them.