Hi Raysør, I think the mod already does this, at least I thought it did, if it doesn't unfortunately I don't have the experience or knowledge required to make what you're asking for.

Hi, I really like the idea of this mod. Since I have limited skills in modding myself, I’d find it challenging to create something like this. However, if you’re up for it, would you consider making a mod that allows global team XP—or at least a portion of it—to be shared with followers, especially the Conjurer’s skeletons? The Conjurer is my favorite class, as well as a favorite for many players, but it’s almost unplayable in multiplayer, which is a shame.

This is how the game already behaves, but I suppose if you roll back to the 3.3.7 build, this mod could still be useful.