Dream Mentor quest is such good magic exp, yet so difficult for people without good defence or don't have proper melee armor. I've done this quest with farcasting myself, and here's my techniques, hope this'll help = )

 

 

 

First, tank over the first boss with whatever you have, range/mage/melee, whatever. Since it can attack both melee and over distance, there's not much point farcasting it. You probabilly will use all your food here if your defence level is low, but that's not a problem.

 

 

 

After first boss dies, you can start farcasting. I personally did this with Ice Blitz (didn't have barrage back then >.< ), and it worked quite well. I believe anything that does 10 second disable works also, just a little harder. After you fix it in place, you can change to range gear and cheap shot it till death. If the boss stats to move towards you again, simply disable them. The timing is approx. 2 magic casts/crossbow shots or 5 shortbow rapid shots with 10 second disable, and 4/9 with 15 second disable, and 6/13 with 20 second disable. The boss moves at the speed of walking, and you can just run around, since the area is reasonably large. This way, you won't need anymore food after the first boss. You do however, need a little experience in micro controlling your character.

This method also works for RFD bosses. I've done them the exactly same way.