I'm fairly sure the Campaign mission they showed off at E3 or w/e the hell it was awhile back was the third mission, where you first meet the Prometheans. Which recently Frankie said Knights are slightly harder than Elites were, so any encounter you have a Knight will be "harder" than past games where it was an Elite. On top of that, Knights spawn Watchers, Watchers spawn Crawlers, put up Hardlight shields and catch grenades to defend the Knight and they can even resurrect dead Knights. So with that information, it's quite obvious it'll be slightly harder.