Ok, I don't understand the whole heal your own group thing.  You can watch anybodies health bar in the raid as easily as your own group, in fact I put the people up on my screen by priority of who is going to need healing.  Tanks, then clothie dps and clothie healers, then druids, hunters and rogues and melee dps.

With target of target on I can usually switch to a mob that is away from the tanks and see who is getting hit and try to stop the bleeding so to speak before they die.

In fact, I hardly look at the big portraits of the people in my group since where I put all the other healthbars of the party are below those portraits.  On trash, I think the overhealing is normal and makes little difference.

Meshach's strat is great though, I always try to have my mana efficient larger heal casting in an important fight, and am ready to hit escape or move to interrupt it at about half cast or 3/4 cast if I see it's going to go off and overheal a bunch.  That way I'm regenning mana as per the 5 second rule if I don't have to cast and I'm hopefully shortenign that cast time on my bigger heal when I need it since it's already been fired up.

One last thing that helps me, with my larger cast spells I found.  If I have my larger heal casting on Dread, and I see Zeph is pulling aggro (surprise surprise) you can change targets mid cast, my heal will go off on dread and I'm already targeted on Zeph to hit the button.  You don't have to wait for the spell to finish to switch targets and the heal will still go off on the target you had when you started the spell.

Back to the heal your group thing.  I guess I can see it working to keep the guys topped off that are in the back doing dps, or not in the main part of the fight so you and I don't both heal zeph when he lifetaps or a healer pulls aggro...but yeah.  I think it's also dangerous to have each healer only responsible for his own group.  I do think I misunderstood it though partially.

I'll keep thinking about this....good replies though