Gyro ball does damagae based on how slower you are and your attack, shuckle has the highest def and is very slow. you use power split to switch att and def stats, after boosting it with curse, also lowering your speed. if you're paralyzed you're even slower. if the enemy boosted their speed its even stronger. you get the idea :P

Sounds very complicated, but Shuckle now sounds like a fukken TANK