It wasn't a failure, especially not at 4.0.
However, it's important to remember that of all the new kit WHM got with SB. All but one of those abilities were almost entirely forgettable when the expac hit. Thin Air was a powerhouse right from the word go and honestly that one cooldown carried WHM for the entire expansion. The rest of the kit was barely worth the screen real estate it took up and this was the case for far too long.
An Expansion where you literally may as well not bother to hotkey most of your new abilities is a failure imho.
*edit* I should probably also note that whilst WHM wasn't a failure on 4.0 dropping. SCH most certainly was. I stand by my comments at the time that whomever it was that signed off SCH going live in the state it did needs to be kept well away from touching any job or class ever again. Clearly that didn't happen though eh? =(
This whole mush kind of reminds me of the situation Everquest's Shaman found itself in somewhere around the Planes of Power/Dungeons era where an entire new level cap toolkit was quite literally a cut and paste of the previous tier, to the point where Verant/SoE actually forgot to modify the wording in the tooltips and left the old names in there to really rub it in. It was probably a good thing that they didn't have an official forum back then =(