No. I think bad writing/design is not do the conflict in the most dramatic place, in the Nightsong lair. If the spear issue would come there in dialogue and the only way to get past in that point would without Shadowheart attacking would be a) have the spear b) successful persuasive check, (very hard one), that would be ok in my book. How they did in this case, was not good game design or good writing.
You're asking her to spite her goddess for no other reason than being too lazy to get her the spear. What's next, do you want to persuade the mind flayer parasite to just leave your head after you jump out of the pod in the nautiloid and the game ends straight after character creation?
True, but do not make my points less valid. They should have designed all companion quest in similiar quality like Lae�zels. (She had her own map/area for it.) I have never been against of idea of plot going foward, but the design decision of important companion quests, making them like they are just small sidequests. Wyll had rough time in his companion quest design also in Act 2.
They will for the most part in act 3, which in my opinion is much worse. I prefer it if they're relevant to the overall story, not just their own little side stories. It makes the world feel more alive.