I think there's definitely something wrong here ....
Did two Infected sieges so far. The one at Kenn Farm seemed okay. I ended up at the #1 slot with 43k after killing a Hulker (which gave me 22k points, I think).
Then I did Diablo Station ... that one was INSANE! It ended at stage 40 and they flew by so fast that I had trouble killing a single one of the Infected with my SMG ... and using a Ground Pounder was impossible because the stage was over before I could detonate the charges.

