I figured I'd jump in on this. As a experienced healer in most games, yes keep your party up at all costs. The problem isn't your agro managment its your choice of ability, try using a less effective heal nuke, use your lower healing skills vs higher healing skills as it keeps agro down and keeps the over heal to a minimal (over healing doesnt do anything) heal at 50% not 90% you just need to keep them alive not 100% all the time, its nice being 100% but its not nessisary. The other thing, your tank should be able to hold agro over you easily I havn't had a problem with healing yet in CM spec at all. Hopefully that helps (if 50% doesnt work for you try 60 or 65 but dont let them get below 50% if possible )