A mechanic for choosing targets is totally relevant and functional in this game.
Buff/debuff spells are essential in any RPG, and I'm not sure if this will be fixed upon release...
In my understanding, these spells are working this way because of the overpower they can cause within the game, so a certain difficulty was created to cast them in order to balance these abilities.
However, the buffs that enemies use seem to be well-directed...
BG3 DM likes to make hard times to his players...