UFC 174 was not predicted to be a pay-per-view success. That may well prove to be the case when the final numbers come in. The lack of web traffic and the fact that normally passionate Canadian fans left in droves during the main event aren't exactly suggesting of major interest in the card.
However, the ratings for the prelims are certainly not a disappointment. Jason Floyd of The MMA Report says that the prelim broadcast--which aired on FX as opposed to the usual Fox Sports 1 treatment--drew 784,000 viewers.
The change in network could well have something to do with that number, it's hard to say for certain.
It's still too early for any preliminary PPV buyrate forecasts.