It makes perfect sense to do Triss' quests before Skellige IF you are romancing Yen. The problem is that if you decide to romance Triss we start to see these inconsistencies. Waiting until after Ugly Baby makes up for her not being at Kaer Morhen BUT it makes the Light house scene redundant. If you ask Triss to help with Ciri (she says she will) why do you ask her to Kaer Morhen again? So really waiting until Brothers in Arms makes little sense in another way...
Exactly but it all goes back to how the story almost intends for the player not to romance Triss and say goodbye to her at the port (judging by this, they intended to romance Yen or be alone), if they spaced out the requirements for her quests or extended her story arc then it would of felt better to do a quest with her, then come back and she would have a new quest, then you can meet Yen in Skellige and decide if you want to be with her or not and then come back to Triss to figure out if Geralt wants to be with her.
As much as it makes sense to wait until brothers in arms, if the player does the quest at the party with her before, then she is going to ask for help (triggering the now or never quest) and it doesn't seem right to leave her when she needs help and you could say the same for Dandelion (helping him before going to Skellige). At this point i don't really mind her not being at Kaer Morhen to begin with, it is what comes after all that (except the fountain scene) where the inconsistencies are too much to ignore - and the last third is the part that needs the most work for the Triss content.