Generally there are two classes that are very hard to find in MMO's. Tank and Healers. You'll often see spam for healers in general. but for raid groups, you see them asking for tanks and healers. There's plenty of DPS. Probably because the DPS builds are generally better for PVP(well, easier at least).
Oh this brings me to another thing that MMO newbies may not know.
It is considered bad form to choose "Need" on loot rolls unless it is something you are going to use yourself, not your companion.
"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." Thomas Jefferson