Only have to bot from 100 to 110 if you are buying legion anyways, which you have to buy to be able to hit 110. Fastest would be hunter bc of mail armor + pet.
This.
I just leveled 15 toons from 1 to 100. I did questing until 15 and then DB. From 1-15, nothing comes close to a Feral druid. They get a 30% speed buff in Cat form. Then they get an additional 15% speed buff, somewhere in the 50s to 70s, for a combined total of 45% passive movement buff--unmounted! This helps them move around SO much faster. Over the course of dozens of hours to his max level, that 45% speed buff is amazing! (Since I didn't quest level past 15, I can't speak intelligibly about the speed of quest leveling after that L15.)
Polls show that most agree that DH's do the most damage--or at least they did at their debut. They may have been nerfed, or the CR's for other classes may have closed the gap. Monks do incredible damage too!
I'm running a night elf feral druid and its pretty fast. Prot paladin was fast for manual play but not for botting. Honestly 3-4 hours wont make a difference unless you're expecting to get banned in the same week for suicide botting lol.
Good points again.
IMO it mostly depends on the CR. So many caster CR's just cast these 1-3 second spells over and over. They never capitalize on Instant cast spells, and most CR developers flat out tell you that their CR is only tweaked for max level combat. (That's why I almost never use anything but Singular while leveling.) Another thing to consider is whether the CR has features like Pull More, and whether it correctly uses AOE makes a big difference.
Any class that quickly engage its target will have a HUGE edge in leveling because it's eliminating the 1-3 second casting time that slows down spellcasters. That's why hunters are fast. Other classes that can charge have a big edge too, e.g. Warriors, Monks, Druids. DK's have Death Grip that accomplishes nearly the same, but it only pulls one.
Some people recommend classes that can tank....
Best solution IMO is to RAF 5 toons simultaneously w/DB. You have to buy War Chest 5 accounts, but they're only $15 each and the price may drop come Black Friday (maybe $5 if we're lucky). The 300% xp boost until 90 means you level once per new dungeon if you do and turn in the quests. Of course you'll need a competent computer too, but nothing fancy.