You mean, within the area they've overgrown? But how would they do that? There will be no way to progress past your level in a given environment because either you'd be level restricted or have an enormous XP leap to make.
Upd: the only benefit the completionist could get is to farm all the XP from a given area to the bone and have like a 30% kickstart when entering the new area. So they could get next level just a little faster than others. That is what I meant.
Because there are many side quests (a good thing) it is not hard to do: I ll argue the goblin camp is meant for level 2-3. See how easy it is to get the three bosses with the bear at level 4? And that's simply by going through the swamp or the risen road them going center. Imagine you do both then center? Without a cap you might be level 5 already. You d probably one shot gut with a fireball. That's the problem.
Hence yes a cap is needed. 30% maybe I don't know. I d go level. e.g. if you are above level 4 you cannot get XP from the goblin camp and get 50% less from the swamp or the risen road. That type of caps
