I think that this season, they really had a chance to survive, but:
1. Christie/Jodi's taxi took them miles in the wrong direction, so had their taxi taken them to the right direction, they'd have survived.
2. I really can't pinpoint Mark/Michael's reasons for the loss, but I think 2-hour penalties the previous leg help cost them the Race. Had one of those penalties not been incurred, they'd have been on the same flight as Kisha/Jen & they'd be bunched up. After that, who knows.