There's a comment at WoWInsider by nearlysober :
"Takes less casts to skillup fishing. At about 260 it was taking me 10+ casts per skillup, after the patch it's taking about 6 casts."
I don't trust the first number (10+ at 260), so I'm not at all sure I trust the second: The classic Noressa/Highlander/Ardeaem/Tedeum data suggest about 8 catches per point. Plus the poster states "casts", and casts have never been what determines skill gains (unless all your casts are catches).
Unfortunately changes to the skill-up formulae are a real pain to test ;-) . Does anyone have any reliable information on this?