But that specific functionality is why they took it out. I don't doubt that they'll add some new mount with some new functionality in the future eventually. But the AH vendor is the reason the brutosaur was removed.
They haven't since added back in reforge vendors on different mounts... and again, they didn't take out the reforge vendor because they realized it being on a mount denigrated the game; they simply axed the whole system. If reforging was still a thing, that vendor would still be a reforge vendor, and I highly doubt they would have removed the yak like they did the brutosaur. Just as they haven't since added back in another obligate water-walking mount after removing the functionality for the strider; they merely made it so players can have that functionality on all mounts.
For your analogy to be true to apply to what actually happened with the brutosaur, there would have to be an example of them discontinuing a mount that functionally did something special (something they've never done before the brutosaur) and then adding another mount that just did that same thing again. Which, like I said, they've never done.
For your analogy to be true to apply to what happened with the water strider and yak, the brutosaur would have to have had its AH vendor removed, which did not happen and then, to play into the "greed" angle you're also harping on, have that functionality instead be added to some shop mount... which didn't happen to the water strider and yak.
So top-down, not seeing any real similarities there.
Buying 5 million gold's worth of WoW tokens is like dropping almost a grand in real life. Of the people that even wanted the Brutosaur in the first place (probably a small amount already) there's an even smaller subset of people that are willing to spend that kind of money on it. In fact, even getting 1 million gold is already dropping about 200 bucks; being even close enough to buying the mount before dropping considerable money into WoW tokens is something that took a fair bit of farming dedication to begin with, which is beyond what most people play the game to do.
If Blizzard was planning on removing the Brutosaur with the hope of driving a sudden influx of wow token sales, I highly doubt that strategy net them all that much money in the grand scheme of things.