Recently I got 1000 kills which should get me lord death(rank 3) but in perks it still says 2, "Apocalypse Aint Got Nothing On Me" came up on the screen when I got the 1000th kill but it doesn't say that in perks and it doesn't say lord death(3) either.

No glitch the rank requirements don't overlap.
Rank 1: 200 Kills
Rank 2: 700 Kills+Rank 1
Rank 3: 1000 Kills+Rank 2
Total: 1900 Kills for all 3 ranks.

Oh okay, looks like I gotta gotta another 900 kills.....this is gonna take awhile