Well, you can't fully respec companions without a mod. So I temporarily installed the mod, and turned Sosiel into a kineticist. Kineticist is a very powerful ranged damage dealing class. Even with a basic build, Sosiel is now as good as Ember in dealing fire damage at range. And with the Gather Power ability, I can now often start combat by casting a very strong wall of fire into the middle of the unsuspecting enemies at a reasonable burn cost. Burn is the Kineticist's resource, but even when he is out of that, his 0 burn abilities are still very strong. He is a glass cannon, as burn diminishes hit points, but unless the enemies have area damage, that usually doesn't matter.

I wasn't even really aware of the Kineticist class previously. It was one of the classes I tried out in the Treasure of the Midnight Isles DLC, which is good to try out new classes. On the other hand, I now also can access Treasure of the Midnight Isles from the main campaign, and the procedurally generated dungeons feel boring compared to the rest of the main campaign content.

While the mod causes some weirdness on some character screens, I am up to now quite happy with the result. It solves my problem that the companions you bring for story reasons aren't necessarily the classes and builds you would want them to be.