Targetting questions, switching targets and recovering from multi-target mistakes?
If dps is not on your target, you are not supposed to be able to hold threat. This is part of the new cata paradigm. The dps is resposible for being on target and this is new for them if they have only played in wrath of the lich king. You have two choices. If they are all on the same target, pick it up and go about your way. If it is one "lone wolf", let him tank it and tell him why he died as the healer rez's him.
If you find that frequently more than one drooler is off target..it might be that they are right and you are wrong. Maybe they are staying on the most dangerous mob that needs to be interupted and your kill order should be re-prioritized. Or maybe that mob was munching on the healer and you didn't notice and react so they are trying to "save" the healer.
In the end, with the info provided there is only so much we can help.
1. Check your kill order
2. Be aware of what's going on around you
3. If one and two are good, bad dps is bad
"he doens't need healing, he doesn't need healing, he doesn't nee-WHAOSHIT!wtf was that man!". Please stop leaning on TDR. -Teng