high rate of AI goals from corner kicks with successful team

So in my first season as Arsenal, AI goals scored from corners were normal. Now that I'm in my second season, having won the premiership and the Champions League, the usual "underdog effect" has kicked into gear (player strikers converting less goals from clear cut chances, AI strikers creating more goals from their shots). This would be fine if it didn't now mean about 50% of all AI corners result in goals, regardless of the set piece tactic that I use. Does anyone have strategy for dealing with this? I would starting using "Defending Set Pieces" as my prep focus, but "Attacking" is necessary for my world class strikers to score on anything other than a stationary ball sitting in front of an empty goal.

What kind of settings and with which players are you using them? How do the opponent typically score and who from your team is to be blamed for the chance?

Details, Ego, details, if you wish for help.

This should be in the tactics/training part of the forum I suppose.

Right now, the wingbacks mark the posts, shorter striker (Persie or Walcott) stays forward, Arshavin/Nasri at edge of area, everyone else man marks with CBR (Squillaci, Djourou) and CBL (Vermaelen, Sakho) marking tall players. The opposing scorer varies, though it's almost always a result of them escaping their marker.

Most people seem to have their fullbacks marking the posts but I don't like that, some FBs are wimps.

I also don't have players marking unless they're good at it. I just use "go back."

My system:

centre backs: mark tall

full backs: man mark

MC (def): mark far post

MC (att): near post

wingers: edge of area/close down corner

strong FC: go back

fast FC: stay f/w

The solution is simply to not use man marking for all players (as robertcornell68 hints). It's good that you man mark their players but there needs to be a few spare players that just occupy the empty space. Go back instruction does just that.

My personal preference is to use fullbacks for marking smaller players as they are usually pretty good at marking, CB's for man marking the tallest players, use attacking players on posts (unless they are good at jumping) and then use only go back instruction for the rest. (Not to suggest that you shouldn't leave one forward and maybe one on edge).

I started conceding fewer goals after I took guys off the posts, giving two more bodies to help get the ball out of there. I put my two strikers on the edge of the area and have nobody forward, the AI teams only leave one defender back and we get a lot of chances to counterattack after corners.