User blog comment:AntiScootaTwo/Advanced Warfare Havoc DLC preview/@comment-1784397-20150113235426/@comment-1187559-20150114112150

Zombies isn't exclusive to CoD, but at the same time it is something Treyarch is well known to do. And Exo Survival is already just a copy-paste of MW3's survival mode, so having something that another game promantly features just makes it feel more like it's copied than anything special or unique.