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.
Regarding playing Act 3 multiple times: Do everything the first time? Absolutely. After that there are certainly things that are just skippable. You know the lore, you know what actually drops loot you need/want. There are certainly discoverable surprises in Act 3 that are out of the way, but Act 3 is just so enormous it's hard to have the energy to comb through every house, mailbox and random book to find them.
