Considering how many barely-started piece of shit games get shown every year, I honestly doubt that Killzone had the worst AI of all the games at E3. It's just a convenient punching bag to help stir up controversy, get press for the magazine, hits for the website, etc.
"Enemies jumping out of cover" isn't even that great of a complaint. It's not like opponents in Gears of War or Halo stay behind cover all the time. The gave GoW 9's and 10's and the AI there will charge towards you in a heartbeat. But hey, these games wouldn't be any fun if the enemies turtled the whole time....it'd just be another piece-of-shit shooting gallery like Call of Duty.