Or we're intended for mana to actually matter, while being appropriately geared for an encounter (which he was not).
Apart from the lack of questing gear, most of this looks to be intended from what they've said the direction they want to take healing.
I remember running OoM in raids, in heroics, in a lot of things really, in early TBC. It sucked, but then I learned to play better and how to manage not only my mana but also my time.
Double Sentinel pull in heroic Arcatraz before it was taken out? If you've actually suceeded at that one pull (those that did know exactly what I'm talking about) you knew that you could handle many things after that.