In 4, I'd Haste first Cecil then Edge, then either Berserk them with my white Mage, or have them berserk themselves with items, (OF course when I think about it, it may have been HAste self with HErmes shoes, then have Rosa bersker them, since I now Can't remember a self inducing Berserk Item)

In V, VI, VII, and VIII I never used it. With the Right Spells Junctioned, you don't really need Haste in VIII (Though my memory is a bit shoddy, so I could be wrong on that front.)

IX I hasted the Caster first. X was all about Hasteaga.