W8 is *very* hard on parties that change classes, especially for one with all class-changers like you describe. I think they overcompensated for the uber-characters you could make by switching back and forth in previous games.The single level/xp system is nice - say for example a lvl 5 priest changes to a lord, the chararacter would need the same amount of experience to go from lvl 5 to lvl 6 to become a lvl 2 lord - but this otherwise elegant idea is *killed* by the experience-based spawning of monsters (depending on how much experience you have, more and more difficult monsters will appear in the same area).
If you switch classes too much or even at all your party will be too underpowered to face the spawned monsters. I tried a party like the one you described and got continually hammered on the A-T road by juggernauts (the elite modai - well more that I think I deserved, but then again to me in an exploration, conversation, item gathering game like this you should never be brought down by such trifles as the monsters or leveling).
- John 
Prepare Yourself for the Ultimate in Fantasy Games