>>718177697
Other anons point this out, and anyone who played the game should know this too: being a slightly decent person to most of the companions improves their approval rating with you which feeds into their likelihood for romance.
That, in conjunction with doing their quests, can usually lock tight their approval. In my first playthrough, I basically took up any good aligned quest I could. Despite all its mid tier writing, the core gameplay is pretty fun, so I wanted to see as much of it as possible.
The fact that Halsin will visit you at night to proposition you just because you did a heroic thing that happened to align with his interests is just bad writing. It's clear that they wanted to put this stuff in but didn't have enough content to stretch out the relationship building so they just put the capstone on super early.