The lack of reactivity at companion quest endings is also a pet peeve of mine. It's not just Shadowheart's. I'm going to just stand here with my arms crossed
while Astarion vents the rage and sadness of 200 years.
Someone should make a compilation of Tav/Durge just standing there with their arms crossed while someone is dying or crying right in front of them, with the last scene being our companions doing exactly the same as Bhaal does his thing with Durge.