Now I might have missed something, or don't understand something here,so don't be super harsh, but compared to enemy players, or compared to what I find on the internet, my mercenaries on lvl 30 lack stats.
e.g. enemy Samuros come with 11atk 71hp, enemy Varden Dawngrasp with 7 attack 80hp and so on
All my mercenaries lack exactly 1atk and 5 hp in comparison, so my Samuro e.g. is 10/66 as seen below.
That was against pretty much mirror matches as well, so I couldn't really find a piece of equipment or anything that would add 1atk/5hp to their stats from the start, but maybe I missed something there?
Now maybe you need to do something to unlock these extra stats or something? No clue, I'd appreciate a bit of help ;)