Personally, while 'efficiency' can be satisfying, I don't usually find it fun. Doing nothing but running around from fate to fate (when a fate in the area is even up) might be the most efficient way to level up, but as it seems to be suggested in this and other threads, it's not very fun.

My personal solution is to not care about how 'efficient' my time is, xp/minute or some such craze. Instead I'm just gonna queue up on one class, and then do fates,side quests, class quests, leves, hunting logs, switch to a crafter or gatherer class, etc. Because I find those fun. I don't care about my xp per minute, so I guess, lucky me or somethin'.