Right now, the fact that Shadowheart only has medium armor proficiency while having a stat layout more suited for heavy armor clerics makes her extremely fragile. Also, Lae'zel's and Astarion's lack of INT pigeonholes them into one archetype. I would suggest swapping their stats around so that these companions have more build options, although this is less of a problem for Astarion once the assassin archetype is implemented.