Agree that Cisse has a poor season so far but why bring him into this particular argument.
The front post is a vital position when defending a corner. We should know, we always hit the oppositions. Didier Drogba was excellent at it, a real wall. Heck, even Robin Van Persie is very good at it. It can make a big difference to the number of goals conceded from corners imo.
You normally want an attacker there because they are used to attacking the ball and not good at marking.
Cisse is rather crap at it. Carroll is superb at it.
Why should he defend the near post in the first place? That is usually a job for one of the fullbacks. Cisse should be up front providing an outlet in the event of a counter-attack. If we have everyone staying back for corners, every ball we ping out will just come back in again inviting more pressure.