HMW XP Tactics

So I have a question. I have been building up my characters again and trying to set up my tactics so that I can have successful builds. However I have noticed that some people that could have leveled a long time ago have not. For example at level 0 I have seen some people with over 300k xp and they are still level 0.
So my questions are as follows:
* Is the experience better at lower levels and there really isn't a point to level up
* Is this the best tactic? I mean to sit on XP so that when you go to the next level you are already maxed out?
I am sorry if this has been covered already, but this tactic has me stumped and I am not sure how to go forward as I really hate to constantly loose and since this is a game I am still trying to learn some of the best tactics.
Thank you for enlightening me.
So my questions are as follows:
* Is the experience better at lower levels and there really isn't a point to level up
* Is this the best tactic? I mean to sit on XP so that when you go to the next level you are already maxed out?
I am sorry if this has been covered already, but this tactic has me stumped and I am not sure how to go forward as I really hate to constantly loose and since this is a game I am still trying to learn some of the best tactics.
Thank you for enlightening me.