Recently, Halo games have become increasingly less viable as a competitive title at the highest levels. Starting with Reach, the inclusion of armor abilities like jetpack and armor lock changed the game in fundamental ways that were too big to ignore.
Halo 4 went a step further. Though they scaled back a few of the armor abilities, they still exist and mess around withpivotalyimportant parts of competitive Halo like line of sight. At top levels, players used to know where anyone could be on a map, where they could hit them from, and where they were likely to run to, but give them a jetpack and suddenly all that knowledge goes out the window.
The real problem with Halo 4 is that it introduced more randomness than ever into multiplayer gameplay. That might be perfectly fun for regular players, many of whom were proud to announce Halo was back! with last years new game, but its vastly different from how Halo used to function for pros
Looks like the honeymoon period of Halo 4 is over. 343 blew it and Halo succumbed to CoD.