Huh, I've never felt that Shadowheart was the creator's pet - if anything, I thought that was Gale's as he has the most extra mechanics and unique story details so far:
- Gale has a unique death cutscene + necro effects + unique ending if you leave him dead - he is the only companion that literally has plot armor
- The artifact eating system is a tracking system unique to Gale, and seems to potentially scale with the rest of the game (i.e. more areas more items). In the EA you can already get a potential story branch/outcome if you ignore him, which hints at a larger quest
- I feel like many of his dialogue scenes involve way more cinematography and special effects (i.e. mirror image, his Mystra story). Very memorable.
Other of that, I think Astarion is the only other companion with tangible unique mechanic (vampire water weakness + bite). In general, I don't think the gaps in the companions have been massive, but some definitely have more going on. I feel the recent patches have brought Shadowheart closer to the top in terms of content, but she was one of the more unfinished companions when we first saw her in the EA (i.e. other than the random hand glowy thing, she really does nothing much later on).
EDIT: I agree while the artifact is super plot important, I don't think that necessarily makes Shadowheart important. I don't know if Patch 6 changed, this, but previously you can easily kill her and take the artefact and just progress the story as planned.
