I give you wrong.
I think that programmers have reduced bonuses on mercenaries, because time ago, even with new skills implemation, I had found easily good mercenaries.
Now, It is impossible.
For example, i just now was seeking a mistic tier 7.... he has healing skill at 5, and healing at 5.. Stop, nothing more...a tier 7 so...??
time ago, was possible find healing skill at 10, with healing 10 at tier 5... now at tier 7 i found this one...