Augur is really annoying to pug because the end phase is the strick check while the first few phases are the confusion checks that can wipe a pug group a couple of times before you clear up who's stacking where for the frost cleansing. So you can spend a lot of time in a group and then only later realize that you either can't kill it or it's going to be extremely tight so you'll be risking a long series of low % wipes in a long fight.
On most other bosses you can usually judge right from the start whether the pug has a chance of killing it so you can avoid wasting an hour or two on a group that disbands without killing anything.