First off, I don't think you quite grasp the barrier experience creates in SoD. Your play style is pretty different from the majority of people. Most people just want to hang around with some friends and slay dragons. At some point in the game, you start needing (at least in the minds/eyes of guild recruiters/leaders) lots of exp to continue progressing in the raid game. I have known numerous people who quit SoD because they didn't have the time or didn't want to commit the time to gain the exp points "required" to continue raiding. SoD has been around for a while, and people who have been playing consistently for years have had the time to accumulate massive amounts of exp. Now consider someone new entering the raid game, they raid a lot and get into a higher tier guild and suddenly they are expected to get to the same experience level as people who have been around for years. Its no surprise that the only people who make it are ultra hardcore, and others who can't see putting in that time often just quit.
Also just LOL at your adv band argument.
Adventure bands are OK because someone else works to give another player/character free exp they didnt work for.
Grupo situation is NOT OK because someone puts in the extra effort to box a tank along with their own character, and grupo gets exp he didn't work for.
Sorry, but in both situations someone puts in extra effort so that another character gets free exp. The only real difference I see is that with Grupo at least there is mutual benefit, since that person can probably gain exp or quest or w/e at a faster rate than they would before. If getting exp w/o putting in effort is wrong, then adv. bands are wrong.
And your extrapolation on guest lock doesn't work. Faction lock will not and should not ever be added. Its too easy to exploit. There is always going to be a level of risk in sharing info, that risk just shouldn't include complete destruction of the character.