Check out Clique for all your click casting needs and suplement that with DiToolTip. DiToolTip is a very small mod that allows you to attach the tool tip to your cursor or move it to different locations on your screen and it has a health bar attached.

What I have been doing is using the cursor tooltip to scan the raid/party, when I roll over someone with low health I target them and perform a click cast. My guild as rule heals only the MT and Aoe folks, everyone else is on a low priority heal/ bandage stratagy, so I usually only have a few folks to keep track of.

It is my understanding both of these mods have been tested in TBC and are working fine.