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.