How can I invest on a defensive Steelix?

Question

Steelix is weak to Fire + Water (More Special Moves) and Fight + Ground (More Physical Moves).

Steelix have a -
Max of 354 HP
Max of 548 Defense
Max of 252 Sp. Defense

Should I invest on Defense and HP or Sp. Defense and HP since he was already to much Defense?

Answer 1

The investment should be in HP and Sp.Def, and some in Def for a defensive Steelix.
252 HP / 240 Sp.Def / 16 Def for a more rounded tank.
Offensive variants can forgo Sp.Def and go for Atk investment with Rock Head.
252 HP / 252 Atk / 4 Def (0 speed IVs for maximum Gyro Ball damage) and Head Smash.

Hope I helped!