I want to do three things on alts:
1.) Level (via questing and/or dungeons)
2.) Gear-up quickly at level cap (relative to however long it took my main, via catch-up gear)
3.) Experience endgame in different ways with different roles
What I don’t want to do on alts:
1.) Any kind of content unlock
2.) Separate achievements
3.) Collect anything that isn’t class or race-specific
4.) Questing beyond leveling
5.) Professions (this is a new situation as of this expansion–I no longer have time or inclination to touch crafting on alts–the new system cured me of that)
Solution:
Nearly everything at this point in Retail should be account-wide, save a few specific things for different characters. This would include:
1.) Leveling and quest completion (but with an option like Threads of Fate to auto-complete all quests at level cap, except class-specific ones if not completed on another character of the same class–think class hall stuff).
2.) Gear (because gearing-up alts, like leveling, is part of the experience of playing a different class or role)
3.) Professions–probably, although not with the Dragonflight professions system. As it stands right now, I’d rather have account-wide professions or just to forget about them as a whole, but that’s more of a DF profession time-gating issue. Although personally I’d be happy with account-wide professions, I realize this could be controversial and many prefer different alts for professions.