Yeah, I'd like to see a new mechanic aswell.
I remember playing Zelda: The Ocarina of Time, which had a pretty awesome fishing mechanic.
I don't remember exactly how it worked but here is my idea for WoW:
Remove the random place generator where the bobber hits the water. I think it would be way more fun having to "aim" yourself. Like facing an exact angle and pressing a button longer to increase the distance. This might also remove the need for fishing pools to always be within a set distance from the shore.
Regarding the catching of a fish, in my opinion it shouldn't be really hard to implement a mechanic where you have to click at a specific time in your catching process to succeed. Maybe clicking too early will lose the fish and clicking too late, well, that will just be too late. What would be hard i think, is to make this mechanic scale with fishing skill.