I've been playing Valhalla Knights, restarting frequently when I get fed up with my latest party. So far, I've learned that playing without a fighter in my party is almost always deadly. By that, I mean a unit who started as either a fighter or a thief, who is currently a fighter, and who has a shield and plenty of armor equipped. I disregard the strategy guide here and buy all the armor I can afford - it really reduces the amount of damage taken. Besides, there isn't really anything better you can do with all of your money. The inn is cheap and if I let anybody fall in battle, I don't make it back to the church for a resurrection anyway. There's not much point in hiring tons of units, and even that doesn't cost that much.
The interesting thing is that I'm slowly learning how to enter combat with my priest/mage and not get immediately clobbered. While I could cast spells, of course, a priest starts with no offensive magic and I always run out of MP before long. So I've found that I can flank the enemies, whack or stab them once or twice, then retreat - and if I do it correctly, I get my vulnerable spell user out of range of the counterattack.