>>20345833Hp, the only time you probably should invest in one of the defenses is if you've run a calc against a common threat and worked out that you won't survive a hit with 252 in hp and need a mix of hp and the corresponding defense.
People do this a lot in vgc tournaments. Especially this years one due to how over centralised it was.
They also ran calcs in offensive stats to work out the minimum evs they needed to 1 hit ko common threats or in the case where they couldn't one hit ko the threat. They worked out the minimum to reliably 2 hit ko the threat.
e.g. Ray Rizzos
Dreamball Mawile