Uhm, I don't recall ever saying I only want to go Diurnal? Would you be so kind as to show me where I said that? Otherwise, please don't put words into my mouth; it's rude. I go with what's needed. If I see my co-AST has chosen Diurnal first, then I go Noct. If I'm with a scholar, I go Diurnal. If I'm with a WHM, I go Noct. Did you miss the part where I said "I've also been in raids as DPS with a WHM and an AST as heals and I've seen ASTs refuse to go into Noct"? Yea, that means that's totally me wanting to go into Diurnal!
I'm saying that from what I've seen in 24 and 8 man content the default setting seems to be an AST comes in and without even checking to see who/what their co-heal is, pop into Diurnal and some of them have refused to switch. If I'm going as AST in something I take the time to check and see who my co-heal is, and if it's an AST who has yet to choose a Sect, I reach out in party chat and ask them which one they want to take. Shocking, right? And here I am, according to you "infuriated" that they've chosen Diurnal because apparently I want to be in Diurnal? I don't care what I'm in.
Also, I said it was frustrating, not "infuriating." Two entirely different things. I'm not "infuriated" that someone chooses Diurnal; I'm frustrated when they seem to think it's the default setting and then 100% refuse to change.