Example:

Fighter kills a yellow con mob for 10 million experience. But, the yellow takes him to half his health. He doesn’t dare attack another yellow knowing that it could kill him if he doesn't rest first. So he rests for a minute and pulls another yellow mob and once again, receives 10 million experience.

Now say he pulled a blue con mob first. It’s worth 6 million experience but only takes him to 3/4 health.

Knowing this, he could pull another blue con without resting as he would only be at half health and would receive another 6 million experience points.

In the same time it took to kill a yellow for 10 million exp and rest, he could have killed two blues and received 12 million experience.

Leveling tip #2:

Killing more of a lesser con will yield more experience. DOWNTIME is the leveling killer. Minimize your downtime and you'll level faster.