Is energy always conserved?

I don't think this is a very good example of energy not being conserved. It seems to me that dark energy would perfectly explain the loss of energy of the photon in this case. The outward "pressure" from the expansion of the universe came from somewhere (Big Bang? Entropy?) and is effecting the momentum of the photon. 
Momentum is p=mv and velocity has a time vector that is primarily what is being altered (the time between the high and low energy levels of the waveform of the photon) giving the same total "mass" of  the photon over a longer timeframe resulting in a lower momentum being given to the receiving electron. (Basically like a mountain melting under a skier - they will have traveled the same height as they would have if the mountain was as steep as it was when they started but they travel a farther length to reach the bottom resulting in slower speed at the finish line.)
So while the photon may indeed have it's energy reduced, it seems like it is certainly going somewhere.