Well, some quests cannot even be completed if you have only "Doom Upon the World" left because some enemies do not spawn anymore (for instance Weed Out Bandits in Crestwood was bugged for me this way). Basically if you only have the last quest to do, the world becomes weird for some reason and quest things don't spawn anymore.
So I hope you have a save before What Pride had Wrough (Mythal Temple).
If you are going for a completionist playthrough I suggest you do everything before starting What Pride had Wrought, at least the quests.
The collectibles (bottles, mosaics, astrariums, shards etc) can be done also after the end of the game.
The DLCs can also be done after, with the only difference that of course you will not have Solas (and Cassandra if she is Divine and you don't invite her to come back to the party).
Trespasser ofc can only be done after 