Also make sure the clutch bearings are not rotating in the cavities of the clutch bell. I have seen some bearing / clutchbell combinatins that will do this. They will blow every time.
Clean them out... Are you actually removing one shield to help get the grease out? If not, try it.
Oil them lightly... We are using a light oil sparingly and replacing the shield.
Space them good... We have begun using Traxxas Teflon shims for all of our inner race duties at our LHS. Leave some slop and these things will provide a little flex as well.
We also use a big shim over the top of them like the OFNA stuff.
Gear mesh should have a little slop but as stated, be consistant all the way around. Dry lube on your gears will reduce heat further.
If you are heating that much, it sounds like slipping is the culpret to me. Try roughing your inside of the clutch bell. Use a temp gun to tell you what it is doing. If it is slipping too much then adjust it or your power plant.
BTW - All bearings will work if you handle them right. I do like the AVIDs the best because I rework them on the rubber shield side and then put the metal shield side towards the chutch shoes. Extra peice of mind.
Hope you get fixed.