Didn't know phoenixstyle did mass invites, but I use oRA3 for that, it also auto-promotes people based on rank or specified names, and auto sets a master looter. It also has a handy ready check display window. As far as something to organize groups, I've never found anything but would also find that really useful if anyone knows of something.
Just did a quick google search, found this (never used it):
http://www.curse.com/addons/wow/auto-invite
Might work. Or might not, depending on how old this part of the description is: