I was looking through my locked achievement list and saw that I still haven’t unlocked the Warlord achievement. You have to win a game of warzone on all three original warzone maps to unlock it. (Escape From A.R.C, Raid on Apex 7, and March on Stormbreak). Thing is, I’ve won multiple times on all three of those maps. Yet, it still says 66% completed. Anyone else have this problem?
For some reason your warzone stats from your service record says that you’ve never played on March on Stormbreak.
As you can see in my service record, I won more than one time at each map, and i have a 33% progress at the “warlord” achievement
As you can see, I am not the best Halo player, and its really frustating to try it over and over again, and see that im not going anywhere…If any one could help me, i will be really cool! Thanks a lot, and excuse my bad english XP
Same problem here. My progress tracker is still at 0%. I won more than once on Escape From A.R.C (5 wins) , Raid on Apex 7 (3 wins), and March on Stormbreak (2 wins).
My friends encoutered similar problem (no progress in the achievement tracker). The achievement seems to be glitchy for some players, but others unlocked it even today (Warlord Achievement Winners).
This is the only achievement I need for 100% 
UPDATE (17/09/2016): The achievement popped for me. I simply played on every map needed for the cheevo (1 game won, 2 games lost). Check if this works for you as well.