My thoughts on migrating camps are:

* If a gladiator or marauder is on the lower level end on the party, they should usually avoid tanking (35 gladiator getting hit for 300 damage vs. 40 archer getting hit for 120 damage)
* The gap between the highest level enemy and the lowest level party member is not more than 9~10 levels (that stray hit will nearly insta-kill them).

Which has the side effect of having a narrow party gap to yield overall improved results.

Although my philosophy is: some XP at a steady rate is better than not getting any XP at all.
And a somewhat destructive philosophy of: if the level gap is too much, I encourage higher level party members to find a party suited for their level, but to remain with us until they find that party.