Something to be careful with if you have a lowbie healer in your group, they will be hard to keep threat against. I have used an 80 druid many times for boosting and a few heals from a lowbie has often caused a wipe as I get a random mob breaking aggro and killing the healer and often then turning on the rest of the lowbies.
There is nothing worse than having a huge pull kill your lowbies before you kill them and lose all the experience because the lowbies are dead