So many times it happened that I tanked adds with my BRD or SMN (it also happened i had to take out Titan-egi for adds), (or in CT it doesn't matter if im in as tank or dps, I'm always on tower duty). As a tank I don't mind taking over adds, I actually prefer them over MT; I have a feeling that I won't be able to keep the boss on me, while I seem better with adds. (ok no I hate the ATMOS adds in CT)

And as Aldora said I noticed also that sometimes healers don't heal their MT, I have actually no idea how people play, but in the end I try to help as best as I can depending what DPS class I am in.