I'm running Landsknecht, Fortress, Medic, Sniper and Runemaster. Considering dumping the Fortress as he's completely useless as far as I can see. Protectors in Untold seem much better. My only options right now seem to be to grind regardless..
This is literally the exact team I ran and while I had a bit of trouble early on, it's a solid set up. Landsknecth and Sniper work miracles together with Squall Volley/Links. The Runemaster can also be nice to getting links going, but the Sniper's Squall Volley will most likely be all you need to really take advantage of it.
If I may offer advice - I wouldn't drop Fortress, personally. They may not be useful for actually hitting things, but being able to soak up damage in place of other party members was incredibly useful to me. Not to mention that they get a skill that can negate one ailment shot at the party (I think it only works one line at a time, but it's still good) for up to 3 turns. I dunno though - if you find a set up with something else that works better, more power to you.

