This is a great example of just how bad the scoreboard really is (or how fake it is). The weights mean nothing, and even though a player higher up on the scoreboard is going to more than likely have more XP than a lower player, that doesn't mean it is accurate or correlates in any meaningful way.
For straight-up XP, I have found maxing the ribbons (3x per) is the best way to get max XP. Obviously, recon gets the Intel ribbon quickly, Support is the only one that can get Logistics, and gets Wingman pretty quick with some combat. So if you start with Irish or Falck and play aggressively, you can have objective, wingman, logistics, and combat completed, then switch to recon to complete intel (which should be partially done already).
