They're singing live but all the micophones are really low except for Chester and Mike, so you can barely hear Phoenix or Joe or Brad. It's very obvious that the gang vocals are mimed. Also, I'm almost sure that the 'ooohhh' backing vocals on Waiting for the End and Burning in the Skies are also mimed and Mike sings over them. And for this summer tour, I realized by listening to the DPS's that the chorus on When They Come For Me also has sampled vocals and Chester sings over them (this didn't happen on the previous tours; you could only hear Chester)
Regarding the tour, I think it was acceptable. I mean, the band played really well all the song, Chester was on top and besides the KROQ show, they had a lot of energy on stage. The bad thing is that the tour became predictable. We pretty much knew all the songs they were going to play and the only surprise was the piano version of Rolling In the Deep (and RME over BIO, if you want). What Mark mentioned is also important. The band didn't talk too much to the crowd besides the 'usual' stuff. But well, I'm sure most of the people who attended the shows had a blast and I guess that what counts.
I hope the Asian Tour can bring us some new stuff, but I prefer not to expect anything.