If I remember correctly the tavern defence, the Pallys of Irabade are protecting the door of the tavern with the civilians inside, making a shieldwall there. There are also allied men-at-arms fighting with you in the yard and archers shooting at the enemy hordes from the roofs while you are fighting the demon and cultist waves. They do not have the manpower to do it all by themselves, at least that is what I understood.
IMHO it makes sense. I mean, it´s an RPG game; would it be more immersive if the fight is over when you arrive and you do not get to fight? Or if you arrive tired and without spells, because you cannot rest, like the fight against the defaced sisters in Kingmaker?
None of which you propose addresses my issue with this fight. A simple solution would be to have the paladin and her troops defend the area by letting them move to attack, and then return to hold position. Instead they are standing there like dummies, as if it was a comedy sketch and not a battle.
