I use Eder as the main tank for engaging the biggest threat. Kana will fight alongside him once the bad guy’s attention is on Eder. Pallegina will tank whatever other threat needs attention along with my wolf, and if there is only one caster my Ranger and Aloth usually explode him/her is short order.
If there are two casters, or multiple ranged threats, I will send Aloth off to the side at the start of the battle, then have him hurl a Fireball, Lightning Bolt or whatever that stream of fire spell is into the rear line of enemies, which usually is enough to kill one outright and damage the others making them easy pickings for my Ranger. I’ll keep the wolf back to guard Aloth in those situations, and possibly use Durance to finish some off as well. Both Eder and Pallegina can occupy multiple melee targets with their proper effects up, so I don’t usually have to worry about them until the ranged/casters are mopped up.
None of this would work nearly as well without Durance. That dude is a lifesaver. I’ll have him drop 2-3 buffs (DR and resistances) at the start of battle, then use either his knockdown spell or the one that freezes enemies while boosting allies stamina. In tougher fights, Consecrated Ground is a must for the stamina restoring pulse every second. Given that he’s also somehow become my best secret spotter (“and the flame reveals something new!”), lockpicker and trap disarmer…I can’t let him go at this point no matter how annoying he becomes!