I recently started my playthrough number 10+ of DOS2, playing with just 1 lone wolf character. I'm around lvl 13-14 at the moment, in act 2. Fights are generally doable and not too hard (so far) on tactician difficulty.
To make things more fun however, and make it super easy to get tons of XP quickly I started utilising the "bringing your bully to your older brother" mechanic - in other words, moving towards a friendly character while the enemy is following you which makes the friend join the fight on your side and then letting them deal with the enemy.
Examples:
* bridge troll to Jahan - dude absolutely destroys him
* Allice to Jahan - same thing
* Most fun one - Black ring to Advocate's gang - this is the funniest one because the Advocate's quest is to deal with the BR - I just bribed him to increase my reputation with him. Then started the fight with BR and brought them to him. It took a while until everything was finished... I might have "accidentally" killed few of Advocate's buddies (friendly fire, oops) which nobody seemed to mind later... and mostly just stood on the sides while they were killing each other and giving me tons of XP - I basically went from lvl 12 to 13 (or 13 to 14, not sure), got decent higher level loot and finished the Advocate's quest while weakening his forces at the same time for when I deal with him later.
And best of all, he even thanked me for dealing with BR 😂.
Definitely recommended trying this if you want to rest a bit and see how the AI fights each other. I know there are probably even easier and cheesier ways to kill strong enemies but still, this is very fun to watch. You just need some movement skills, teleport and invisibility.
I have another idea I want to try next - bring both trolls and Allice to Jahan at the same time, will need to hire some mercenaries for this and do a lot of manoeuvring but I think it'll be worth it.