Well, +4 Atk Shuckle has a max Atk of 390; with 75 and 90 BP+STAB on the 4th & 5th hits minimum, that could hurt. But with that kind of setup necessary, I'd rather go with some gimmick set in a Trick Room/Sand Stream team that includes Power Trick to take advantage of a Rollout off of a potential 614 Atk. (Shuckle can attain 614 Def and a Speed of 13 with 0 Speed IVs/EVs, max Def IVs/EVs, and a Relaxed nature.)
Of course, that assumes that I understand everything correctly. (It's amazing how many of the little things I have become aware of since I've started battling competitively. And I thought for the longest time that I really knew Pokemon... XD)