Note: this mod requires EEEx

Tired of your triple class bhaalspawn lagging behind in levels in a party of 6? Playing with tons of quest mods and no XP cap but can't guess how much you should reduce XP? This mod solves all this by letting your party members gain XP at different rates that you can adjust on the fly. You can configure each party member to gain anywhere from 0% (no xp gain at all) to 600% XP. Applies to all incoming XP from any source (quest, kill, special events, etc).

This is done through a book item — "Tome of the Masterful Learner" — added to the protagonist's inventory at game start. 

Very lightweight, with EEEx being the only dependency. Can be installed anywhere.

Download: GitHub

Discussion: G3, Beamdog