There's a thread on WotC boards in "What's a DM to Do?" and somewhere here on ENWorld by "smeelbo" -- and somewhere in the thread, he found someone who had done their best to errata all the pre-gen characters, and posted up fixed sheets for anyone to download.
Apparently, all of the characters who had "Weapon Focus" (damage: +1/tier) only had factored in +1 to the damage instead of +2 (for being level 11, and thus, paragon tier, 2nd tier, earns that extra +1).
I don't follow how you or anyone here in this thread did the math, but you do seem to be coming to the right conclusion.
Check out that thread:
Tips for DMing PHB2 Release Day Adventure. You can also find a bunch of other useful information about the quest that people had questions about.