When we were first learning bloodeye we had some issues with the DT also. We found that a 6 man group with 1 person doing single cures is not going to get 6 players cured everytime. Aka can fizzle, or interupt your cure and bam someone in your group is dead. You can make the curing a little easier by making 5 man groups instead.
Also, clerics should cure themselves. I'm sure this will be debated but I am a cleric, and if a mob can DT, I have a cure ready to land on me. My DT will not be the reason we wipe. Sure pallys/shammys/druids can do it, but suppose they don't get to you in time, and your DT has 3 seconds to go. You can always AA cure but maybe it's down.
The MT is not always the most important person to watch either, let me give you another example. Your cleric has a paladin in group. The paladin forgets to cure himself. Your cleric is grouped with some good dps, well the DT AE fires and the cleric has a choice, cure himself and let his group die, cure his group and risk the MT dies, or not cure anyone and kill the entire group. In this instance I think the best option is to go for the group cure and hope the MT is covered enough by the other healers for those couple of seconds.