I remember grinding out the class quests when going through 40-50. I was thinking on this topic while reading another poster's suggestion about solo players being able to get something in line with what people who regularly raid. It got me to thinking about how hard it is to learn secondary roles while leveling, unless you regularly group while leveling.
I have 3 level 75's (rk, champ and guard), been playing for a little less than a year, and have learned so much more about my classes while grouped and what their capabilities are. That being said, I was thinking that it would be cool to have a class quest skirm that players can solo to help learn the other aspects of gaming outside of solo play.
For example, a quest line for guards that focuses on keeping and building agro with other npc's. A champ line that would help learn how to off tank when needed. A RK line that would focus on the different damage (fire vs lightning) and healing types (single tank vs group). So on and so forth. Quest/instance/whatever could have the mechanics of it set up in such a way as to have them fail if they aren't 'doing it right' ie holding agro, off tanking, healing, and so on.....
Obviously a solution to this would be to group while leveling, and I realize that. But I think it would also add to the quality of in game play. Players who have solo'ed much of the content will at least have a background in how they function in groups. That way there is less of a learning curve when grouped, which should increase the overall competency (hopefully) of PUGS, and also shorten the learning curve for those that level alts to add to kins raiding ability.
Along with this you could add in class specific items to reward the completion of it, some tp, or whatever.