Well I don't think the strategies are really what's hurting you. I wasn't there while you are healing, so I don't know specifically what you were and weren't doing. You use DI, you use potions, and seemed to be on top of things, but you just couldn't keep up. The best advice is to just keep gearing up.
There is a debate on which is harder, Kara or Heroics, either way you feel, they are still pretty close, and you should have kara-entry (or near kara-entry) gear for when you start heroics. There is the Pre-Kara Holy guide that Dil created that should help you in gearing up. Some of the gear he mentions are from heroics themselves, but almost for every slot he has non-heroic and/or non-badge loot that you can pick up in an instance or a quest. Just looking at your reputations I know you haven't done enough of them to gear up properly. By the end of it, you should have another 200 or so healing and another 20mp5 at least.
Not saying it isn't possible to go through heroics, with an awesome tank and awesome dps that can carry you through it, you would be able to complete it, but for an average group, some of which aren't geared enough either to do heroics, you will struggle like you showed here.
Edit:
Actually, YJMark updated the Pre-Kara Holy FAQ in the wikibase, which you can go to
here.
Edited, Jun 30th 2008 1:01pm by CapJack