My team is Landsknecht, Dancer, Fortress, Medic, and Runemaster. I'll start using taunt, thanks. I didn't collect any small flowers yet, so I can't buy nectars, but I'll keep that in mind.
That's going to be a durable front line but not one with much damage. Dancer is support mainly, Fortress is defense mainly (almost exclusively), and Landshark is OK damage (until higher level, with the right kind of setup
and party, then they can do impressive damage). You are going to be hurting with no good way to do either binds or status ailments on enemies. I would drop the Landshark and get either a Nightseeker or Sniper (I'd go with NS, they are crazy strong past level 40 with virtually no setup) but either will probably work.
If you get a NS or just keep your current party, have your Dancer focus on attack dances. Your medic will be fine handling the healing. Get the Dancer's skills to get extra normal attacks and to stun on hit--won't hit very hard, but all those hits add up, and stun can and will save your life sometimes.
If you get a Sniper, consider dropping the Dancer; a Sniper and a Landshark work well together. With a S+RM doing multihit attacks, your L's links will be able to do good damage later.
I 100%'d the game with a Fortress/Nightseeker/Dancer/Runemaster/Medic party so that formation is proven. If you have a Dancer + Medic, though, don't waste skill points having your dancer be a healer (until way later in the game when you have extra skill points). Medic can pretty much
only heal. Dancer has lots they can do.
Tip for your Runemaster, focus on one element and level up TP boost, I always went with Volt.
Actually I would highly recommend you put a few points into every element so you can always be hitting enemy weaknesses and because of how different spells have different formation targeting ranges (all, pierce, row, etc.). You don't need to max the skills right now (in fact,
don't because the TP costs will be prohibitive). Lategame, Galvanic Rune is pretty much king of Runemaster's damage so you'll want to max that.