Sadly yes, from what I can find. It's a good idea -- basically change the merc tab into something like the familiar tab. The merc list has gotten way too long and you can't un-hire any of them. I've tried to figure out a way to "hide" certain ones that I'm not using anymore, but no luck. I think a roadblock with the developers maybe converting it to a familiar-like list is that there aren't any portraits for the mercs. Turning them all into icons would be a heavy lift.
The best I can do is the mini-list: