any hired henchmen will be given the same amount of exp that the main character that you are using to talk to the henchmen vendor. But in order to do this, first dismiss the hired henchmen when you first get him ( he will spawn in the hall of heroes) then hire him again. He will now have the same exp as whoever talked to him (i think). So even if you store him in the hall of heroes and have a 5 lvl gap later, just talk to him again and he will be leveled up to the same level with the same amount of exp.
Yes I do that. But they are missing attribute points.
Like I said, my ranger, after I dismiss and re-add are almost exactly the same. Both are level 9, have same name, protrait, etc. But one has 39 attribute points and the newer one only has 33 total.
*Edit* I should edit and say that after dismissing and adding my new henchmens they get 3 attribute points I can add manually at level 9.
They are missing points from their BASE. Like my old ranger has 7 speed and perception which I never increased manually, but new ranger has only 5 starting base in both, along with less con and other things.