Ok, in Vanilla, there was a big class balancing intiitative. Every major change patch a new class would get their changs, and before said patch the devs asked for feedback from the community.
His initiative was actually quite successful, and a lor of class got some fundamental bad things fixed. So, it comes to the Shamans turn. There is a thread full of good and intresting ideas. However, the CM responsible for collating this feedback was sick the week he was meant to do it, so another CM took over. Our patch got pushed back as a result of this and someone else went in our place.
So next patch comes about, and they do Shaman AND Mage at the same time. Mage gets a good load of stuff and a lot of problems fixed. Shaman get about 1 buff with the rest of the changes being nerfs.
At least I think that is how it came about.
The shaman forums go absolutely mental. Someone suggests that the Dev responsible for this gets 'Hit by a bus', and the term Bus Shock was then coined. People believe that to this day the apparent shoddy treatment Shaman get is a repercussion of this incident
Full archive of all relevant bus shock links here to explain more about the phenomenon of coining this term, and Blizzard's official response and reaction to the bus shock incident. Must read if you played WoW, were involved in the community, and are familiar with some of the community managers at the time.
https://www.reddit.com/r/wow/comments/pid7a/bus_shock/