Level 84

Total Experience Required 3,913,417 [confirmed]

Level 100 progress: 57.33%

This is roughly:
Killing 13,045 people in Warzone, or...
Killing 13,311 people in Execution, or...
Killing 11,055 people in Wingman, or...
Scoring 2,795,298 points in Guardian, or...
Scoring 8,507,429 points in Annex, or...
Scoring 5,149,233 points in Submission.

Horde (TU4)

Completing 19,568 waves on Casual, or...
Completing 13,045 waves on Normal, or...
Completing 9,784 waves on Hardcore, or...
Completing 7,827 waves on Insane.

Or a combination of the above. Have fun!