Ah, so you can actually get the party dreaming option for Wyll. Then instead, his romance is the only one you can actually pursue without starting it in act 1.
He is the only companion who doesn't have an option to start it outside of the party, that might be the reason. Lae'zel and Shadowheart get an approval based dialogue option that starts it, Gale gets the weave scene during a long rest based on approval, Karlach gets an unavoidable long rest cutscene based on approval. Astarion's the only one I'm not sure of because he never likes me enough in act 1, but I think it's similar to Lae'zel and Shadowheart. Wyll never got any dialogue option for me and I never got to kiss him at the party so I assume he's like Lae'zel - if you are already on the romance path for too many others before triggering the party, he's not interested (at that point, anyhow).
So Wyll gets less romance content than all other companions in Act 1? That's disappointing.
What you're saying does agree with my experience so far. I'm replaying my Durge at the moment and really focusing on trying to improve companion opinion this time so I get more access to their content. Wyll is again effortlessly at 100 halfway through Act 1, but with some of the other characters at higher approval I'm seeing way more content. Like Karlach waking me up during a long rest, as you described, something I never saw before. Also, this time Astarion is actively trying to romance me, rather than only having the option at the party if I choose "Knowing you, it probably is". And I saw several scenes with him that I never saw in my original playthrough, like the mirror scene, or him asking whose blood I'd drink. I'm mostly getting the same options as before with Lae'zel, Shadowheart, and Gale. In any case, I have reloaded the party a few times and tried out different choices, and I discovered that taking any romance option with another companion will shut you out of the possibility of having the romantic dialogue with Wyll. This seemed consistent with, for instance, the fact that you won't be able to engage with Lae'zel or Astarion romantically at the party if you already agreed to see Shadowheart afterwards. However, something that didn't initially register with me, but now seems relevant, is that you can kiss Wyll at the party (if you talk to him first) and it won't cut you off from trying a romance with other characters. So I guess trying to initiate his romance sets some kind of flag, but not others?
Why is Wyll treated so differently? Because of his rewrite?
