I had a strange problem while trying to add a henchman and thought I would share my solution.

What was happening: The custom henchman appeared in the list of henchmen as level 1537. Obviously, not being level 1536, I couldn't hire them.

What was wrong: Under the node HenchManData the following line was incorrect:

<attribute id="Level" value="1" type="1" />

..what it needed to be was:

<attribute id="Level" value="1" type="4" />

I got the type=4 from checking the .lsx of the henchman I was able to get added which displayed as a level 1 character as expected. Since the rogue was displaying as the improper level I made its level line look like the wizards, and poof.

Something that might have been related but I changed at the same time so I can't be certain: The rogue had the spell Projectile_UnlockMagic with 0 in witchcraft, character level 1, and 5 intellect. Since I removed that spell from the rogue's .lsx before it was showing at the proper level, I can't be certain it whether was a part of the problem or not.