The lvl 45 give you hands, head, legs and shoes. The lvl 50 give you body piece.
Ok cool thanks, and is all this from the DRG trainer in Coerthas?
I doubt it.
The way it works is you do all the class quests up to level 30 (which is the last one iirc). Then you usually talk to the guild receptionist and s/he'll give you the job quest. You do the job quests for 30, 35, 40, and 45.
Quest 45 is two parts: the first part sends you to four areas (which may be in the same zone or not) and that gives you your 4 pieces. The rest of that quest is devoted to obtaining your 45 ability.
Quest 50 gives you the body piece and your last ability.