Same here. And their stats always reset to default whenever you hire them again but Talents will stay and you have again +2 respec points.

This should be sorted out soon that at least their stats will stay or remove talent points Bug.

If I for example take "All skilled up" Talent, dismiss and re-hire merc he will have that talent already + another 2 respec points. So you basically loose benefit from that talent next time because their attributes and combat/civil skills are back at default.