Can spell speed, and skill speed be combined into singular haste stat?

[Absurdity]

Depends on the class

Every caster besides RDM has a potential spell speed build that could be a conditional BIS if crit wasn’t so damn overpowered, AST and BLM especially have had BIS spell speed builds in previous EW tiers

Summoner doesn't have one either, the 3 different sets it has only exist to ensure you get 6 attacks out of your demi summon depending on your ping. BLM is as always the odd man out because it hasn't been shoehorned into a strict 60 seconds or 2-minute loop.

Warrior technically has a higher speed set but all it does is make your Upheaval drift. An argument could be made for Gunbreaker potentially making use of haste if they nerf crit, because that job drifts harder than Initial D anyway.

Healers are pretty much the only ones that can freely use high haste sets because they have no rotation to speak of and the few skills they want to put under raid buffs are unaffected by a faster GCD.