Now that you mention it, I think Agility is a much better option than Ice Punch. I only taught it that to for Iris but I never got to use it. 10 perectly good shards down the drain... And don't get me started on that catch rate. Trying to catch Metangs in BW has taught me to just Master Ball those bitches as soon as possible. You can get another Master Ball later so it's not that big of a waste if you use the first one on a Metang. Whoever gave these things the same catch rate as legendaries should be arrested.
You can catch a wild Golduck on Route 14 and, even though I can't imagine it will be that much better, maybe it's worth a shot ?