I was rather excited at the new sets inclusion of mercs. So I thought I would share my early experience of them. While I doubt they will be the next meta, they are quite good to play and can bring results if you have the right cards.
The down side is that you will need Ex Fierte to make the most of Heierrat Knights skill, and Ex Yuni if your don't have the new Yuni to really give you a chance.
I've found that starting with Heierrat army and using them to buff Fierte is a good opening. Next Heierrat Knight who works well with Fiefte. Then it's really up to you what you play, but consider that you need the field commander on early to get the most from her buffs. Then play cards that have cheap action skills like Rev Blade, and merc fencer. To try and trigger the commanders second surge skill. I have only achieved this once! I only pack two grims, Rapid Growth and Fire Arrow. For souls you will probably want Dryad for rank up and Delrare for good muti damage.