When I was playing Wrath, I leveled my main in about 4 months. When I leveled my alt, it took me half of that time. Nowadays, leveling is easier. The fastest leveling on any of my alt was 1 month (I work and spend time with the fam).
How fast was your fastest leveling of your alt to max level - any expansion?
2 days. This xpac.
I can go 1 to max in 2-3 days if I wanted and tried. Even before the squish at 1-120 and earlier expansions I could always manage that time.
I was never that fast leveling. Takes me at least a few months to do so.
The only time I was happy with my leveling was when I reached level 30 in a day in wrath, no looms, no dungeons, just pure questing. Felt like I had memorized the best questing routes at the time and used them to my benefit.
In MoP my friend was boxing and farming Sprites in the vale for those epic shard things, i’d sit in a group with him and afk while i watched movies on my other screen and talk crap in vent, typically my characters would go from 1-cap in 2 nights without me ever so much as doing a single quest, i just kept making alts and giving them alchemy for transmute cooldowns lol
I have lots of alts I’ve leveled, but I never play them continuously.
60 dollars
In BFA I leveled my sham in 2 days from level one. This expac, I guess 50-60 release day on my dh. Took me. 6 hours.
15-20 hours /played was my last one I think. I have a ton of xp potions I’ve been hoarding for a while.
Now, that’s the fastest anyone can do it. 
Before Shadowlands, you could breeze through leveling as a Panda Monk in full BoA gear with XP potions…well any monk really, but the added rested xp made it that much faster
I love monk, but I don’t have 5 of them by accident
Before SL when they added that winds of wisdom buff (100% XP increase). That was super fast and it stacked with other xp bonuses such ad DMF, and the old garrison elixir. The buff was so good that you could level fast only with random BGs even when losing
The record is something like 8 hours or less maybe. I can do it at a very leisurely pace in 15 or so.
As far as classes/specs go, I actually find a warrior (arms or fury) to be the best. Ridiculous burst, self sustain, charge + leap, single target or AOE doesn’t matter…even as prot, you are an unkillable god of destruction in dungeons with damage unrivaled by any class.
Just looked it up… wowhead has this guy at 6 hours
They also had this table for speed by expansion if anyone cares…
| Chromie Time Expansion | Approximate Pace |
|---|---|
| Warlords of Draenor | 12 hours |
| Legion | 14 hours |
| Battle for Azeroth | 16 hours |
| Mists of Pandaria | 16 hours |
| Cataclysm | 20 hours |
| Wrath of the Lich King | 24 hours |
| The Burning Crusade | 24 hours |
That’s a long way from
I figure this is what they are talking about when they say “Wow has never been easier to get into” in the adds
I often think I’d enjoy the game more if leveling was more engaging/difficult. It just starts to feel monotonous after a while as it is.
For a normal player without the perfect leveling path mapped, you could probably get up at the crack of dawn, start a new toon, and binge your way from 1-60 before midnight if you were humpin it.
Yeah something told me even 8 hours felt too high.
Still those numbers are assuming people of lower skill level…and no way is Wrath as long as BC…Outlands is the last vestige of the old school quest logic with horrendous drop rates as a norm, grindy as frick quests, excessive travel, and scores of elite quests cutting off entire chains. Not to say other zones don’t have some of those, but none to the degree BC did. I’d say BC content is the only one truly at the 20+ hour mark and anything else can be safely under 20 solidly.
i leveled my hunter back in legion from 100-110 in 2 days. 100-105-106ish first night and then banged off the rest the 2nd day and then spent that night farming gear and then started antoher toon rinse repeat lol… was fun tbh or at least to me cause it didnt take long to level up an get gear too 
older xpacs ( back when i was a teen i can’t even remember the countless 24-36 hour gaming sessions i had jsut lvling and gearing toons on horde and alliance…i dont do that much these days anymore tho… i’ve had my fun with that im a wow boomer now )
Takes a couple days now if you are determined…faster if you are determine and know what youre doing.
I like it as things are, I do which theyd add a slider to slow it down sometimes.
Idk if it counts but when experience potions were bugged (BFA) I level 1 to max level in 4hrs. Bug caused exp potions to stack each time you used one. So the sky was the limit lol.