You don’t have to use a slow 2h to level as arms. It only really affects the damage of abilities you get later (Mortal Strike, Whirlwind and Overpower). Overpower is the only one of those abilities you can use before level 36, before that point there’s no reason not to use a fast 2h like Manual Crowd Pummeler or Gargoyle’s Bite. It’s actually beneficial in some ways, because slow weapons tend to overkill by a lot, you’ll probably kill things marginally faster with a faster weapon until you get whirlwind.
Also the faster weapons tend to be much cheaper to buy on the AH.
Lack of hit chance from gear, Mortal Strike is generally better due to weapon damage scaling vs Bloodthirst only scaling on AP. Access to weapons, and having to replace two vs once.
You don’t suffer from the DW penalty if you decide to play janky and false queue Heroic Strike.
So if you master the art of wiring HS between your offhand hits and cancelling HS before your main hand hits, you will essentially give yourself a ton of hit % to your offhand.
Having a weapon skill racial helps considerably (+3% hit chance), but also people weren’t aware of how effective it was for grinding lower level mobs back in the day, either. With the knowledge of these two things, it’s much better to level dual wielding in a lot of places.
It is, however, not necessary to actually talent into Fury, and I honestly wouldn’t recommend it until at least Enrage was accessible. But you can switch between DW and 2h, and Sweeping Strikes is very useful for opening up on packs in dungeons for threat using a 2h, and then weapon swapping to a different setup to continue.
I’m aware of this, I use it in raids. I think it’s a little much for most people to use leveling but possible for sure. Generally Arms is just better for leveling due to better cleave and Mortal Strike scales off weapon damage (which like it was said before, getting one two-hander is easier than two two-handers).