Why are skill speed & spell speed separate stats?

[Giantbane]

Perhaps to keep in mind for future content (perhaps NIN even, depending if Ninjutsu has a cast time) for melee/caster hybrids.
PLD is another example - since PLD doesn't have any spell speed gear (minus materia melds), it means that casting spells like Stoneskin will be at the default 2.5secs recast.

That doesn't make any sense. Skill speed is already a weak stat, but it would be particularly weak for any class if it didn't apply to all their abilities.

How is a PLD casting stoneskin a few tenths of a second faster imbalanced? PLD already has to full stop DPS & threat entirely to stoneskin, whereas the relative warrior equivalent (self heals) is performed while they do damage.