If u have a level 3 garrison at back in Draenor u can get 4 daily quest to go to frostfire ridge and kill and collect stuff takes a few minutes then u have a chance to get a Elixir of the Rapid Mind http://www.wowhead.com/item=128312/e...the-rapid-mind this will give u alot of xp

Then like u said boost ur toons with the 110, but before u hit the boss in the dungeons take the potion, kill the boss, the toons that u are leveling run outthe dungeon and log out

With ur 110 run out the dungeon reset and then do it again, wait till ur at the last boss, log into ur toons that u are leveling and then run in dungeon kill boss,

Then rinse and repeat!! Very easy and very fast!

SIDE NOTE
At the moment them potions are like 15k each on the AH but with ppl farming the dailies they will be coming down in price fast! keep an eye out for them!