If you're in a big hurry to hit the end do these two things, run each dungeon at least once and complete the quests inside them, dungeons give HUGE amounts of experience for their quests last I knew and que for a battleground every so often. While it's not the fastest leveling, it mixes things up a bit and gives you a break from the grind, and if you're not crazy into the story it's a huge grind.
I dont know why i havent posted this earlier but i have been using Zygor for more then 2 years now and i simply love it! Worth every penny i paid for it. Speeds up leveling process and makes it pain free. And when your max level fun is not over and Zygor will help you every step of the way whether its Reputation grind, daily quests or achievements its brilliant.
Level your hero. You need to start leveling him from the moment you have 2-3 units. This isn’t necessary. If you have KotG, DH, BM, FS, or AM you don’t even have to wait for units. However, with the help of units, your hero can very easily overcome creeps. Among players there is a certain understanding – creeping. Creeping is the destruction of neutral units in order to gain experience. If you kill a creep you earn gold. A gold number and a plus sign will appear on the screen. Sometimes, you need to kill them in order to earn more gold for building purposes.