Are you kidding me? Leveling up was a breeze in X & Y.. so much so, don't have to grind to level up thanks to Exp Share on whole team.. and without any grinding in the tall grass, was able to sweep every single gym, not losing a single time including the Elite 4, champion, and all the post game battles/events. unlike previous generations where grinding was a necessity, especially since exp share only worked on 1 Pokemon and only gave 50% exp instead of 100% like now.
Did you forget to enable exp share?
Also the #1 way to level up pokemon is to drop them off in the daycare.. stick a dime under your thumbstick leaving your trainer going in circles around the prism tower on the bicycle while you sleep. by the time you wake up the next day, you'll have two fully leveled Pokemon.
Then all you have to do is give them pokerus, put on a power item (bracer, weight, lens, etc), do 6 horde battles for the EV your needing, and you will have fully maxed out their EV in that stat. and so on with the other EVs you need.
Each Horde Battles = 50 EV points!!! this is insane in comparison to previous gen.
You can have a 100% fully EV trained pokemon in under 15 minutes only after 12 battles.
While on the other hand, to fully EV train a pokemon in previous generation, 65+ battles was minimum and took over an hour! Each battle only gave 10ev max.