Personally, I would use an in-game parser, but I don't require it.
If they made it so that after dungeon/boss fights or dummy sparring it gave you a break down of your DPS in a results window that only you could see, I think that would be okay.
Truth be told though, I am aware of SE's reasons for not offering a party-wide parser because of the fighting it could cause, but like I said, I'd be okay with it if the results were something ONLY your character could see.