As long as you max your awaken ninjas and equipment then its fine to level. Remember to make sure you don't level too fast by doing the plot instances that you have done before since its easy to do so at your level. I've seen people at your power level but they are at level 73...

People tend to restrict their level around level 70 because that's when you'll face much harder players as some started to understand the game.

He's paying money to be able to get that so don't worry about him. As long as you are able to defeat the typical players in your level range, then you should be fine.