If I wanted to slowly go through a dungeon and my guildies weren't around, I would use the new(ish) group finder tool. I have had great success with it.
I kind of like how the dungeon finder is typically an "efficient" run while group finder can be used for story runs, training runs, etc. I don't see a need to also add additional functionality to the dungeon finder now that we have group finder, personally. Plus, if the dungeon finder queue was split into sub options, it definitely would increase the queue time which would make it less efficient... not a great trade off.
I voted no, here is why:
Normal dungeons instead should be made soloable, as they cannot be buffed as that would make people angry. Allowing them to be soloable means people can truly go at their own pace since group questing in this game is broken anyways (I hate doing it because people skipping dialogue skips it for me too).
Veteran dungeons, as long as the tank and a dps is there, trash can be cleared while the other 1-2 people read npc dialogue and then can get pulled into the boss fight once they’re done.