Usually I'm pretty cool with companion pairing but I think they added some extra touch to Iron Bull/Dorian because it started a bit...icky and rude at best.
For me the Iron Bull is probably the worst written character as far as DA goes...so whatever .
He's there in some limbo where I just hunt dragons with him laugh and then forget he even exists.
I wished we got a bit more with Dorian for sure but you do have a couple of banter where you talk about the future , sort of.
Dorian is also loosing his cool when the Inqui is dying , well as much as everyone is loosing his cool (it's so sudden in game )
He doesn't even tried to reason with a pro Qunari Bull.No melodrama , he's just bitter after his death.
Anyway for me it ends the same , Inqui goes Red Jenny and go in Tevinter to see Dorian from time to time.
Bull stays with the Chargers and see Dorian from time to time.
In both cases scenario , Dorian doesn't want his lover around all the time.He also complain about Bull being a big softie.
The way I see it Dorian is an idealist man on a mission.His first and true love is Tevinter , and his country is in great danger now with the Qunari , and the inner corruption.
The Inquisitor was the hero during Inquisition and Dorian had a supportive role.But again directly related to Tevinter , he stayed because the Venatori and Corypheus wanted to bring the worst out of his country.
If you romance him , you see him at the end at the war table so he's still supporting the Inquisitor 's goal .
He also stayed two years with the Inquisitor after Cory fell .
I think in Trespasser it's just his way of saying "I love you but you're the eye of an hurricane and I want to be my own man , not your cheerleader".
He also says it in DAI , he wants to bring change to Tevinter because he cares deeply.He doesn't want the Inquisitor to follow and beat everyone into submission just because the boyfriend is Tevinter and the Inqui needs a hobby.