It was an "OFF" show for some people, probably people that have seen them many, many times and have experienced much better performances. For me, it was mainly just the lack of vocals that really was a bummer. Tool is a balance of 4 elements, and when you take one out, it is sorely missed and you can FEEL it immediately, if you are tapped into the show like I was. I wasn't drunk or high or anything. I was just there to observe and feel something. Musically, it was just fine. They were really tight for it being the 3rd show on the tour.
I've been in bands and performed live before. There is a reason why Tool plays to sold-out venues every night they play. It isn't easy to come off sounding so amazing. I give them all the credit in the world for what they've accomplished. Its actually way more difficult than it even seems. And yes, there will be OFF nights, and now that I think about it, there's no reason for Maynard to make a comment about his lack of singing or not feeling good. It would just take away from those that didn't even notice. They did the best they could that night.
They are still the best musical group on the planet.