The location of your seats in the arena can have as much of an effect on seat-to-train-seat times as Tube station entrance queues in my experience. From some of the entrances/exits you end up walking almost a full circular lap of the arena before being able to exit the O2 dome building. Though pretty much everyone is heading in the same direction so it kind of works.

Unless there are delays or problems on the Jubilee Line then, whilst the station does get very busy, it is usually a fairly steady flow. Just don't hang around and be prepared to engage in a little "effective queuing".

If you weren't in a rush I would have suggested taking the Thames Clipper services back to Central London (these are relatively slow and expensive, but make for a very pleasant post-concert journey).