CP tell nothing about dungeon-experience, so separating CP characters from CP0 ones wouldn't be a good idea, but I'm pretty sure there is a counter which boss a character has beaten how many times, for other purposes like overall statistics, and so on.
This counter also could be used to add a new matching-mechanic to the dungeon finder tool. If a character (not player) has beaten all bosses of a specific dungeon, say, 5 times, she/he gets the option to only group with other players who have beaten these 5 times too. It must not be mandatory, but a choice for the specific dungeons, so if players e.g. wish to try another role, want to explain the dungeon to unexperienced players or are still unsure, they always should have the possibility to disable this option.
This mechanic would allow players to at least expect the other party members to be experienced too or they have to expect them to be unexperienced (less skill points/new to dungeon/need+read the quests, etc.) - and, most important: before the party is formed. This could reduce frustrations, insultive speech, kicks, aso to a minimum, because it's clear what to expect before and not only when actually performing in the dungeon. Players also cannot just pretend to be experienced, as long as they do not meet the requirements of the counter with the specific character.
Explanations of dungeon mechanics would still be possible, because until one meets the requirements, experienced and unexperienced players would always be put together.
It could weaken the RNG-of-expectations-and-intentions a bit regarding how the tool works right now, where plain level or cp number are the only requirements.
I do not think, that this would lead to a 2-class-community, because other possibilities (friends, guild) to form a party would still be there too. It just gives players more security about what to expect.
What do you think about it?