all generalizations are reductive...the matter is this: sp is,as ele shammy is for eg, a class whit short casts. mindblast is a basic 1.5 cas...that is very short, mindflay is a very short one too...others spells are istantcast whit cooldowns so its takes relative benefits from the GcD reduction.
staking offensive stats is not as like as staking int or stamina where more u have the better will be...
crit has ha crit % haste has a haste rating % and also hit has...so is needes some theorcrafting.
first of all u shouldnt stack haste if u see that u cast spells in less time that 1.1 sec cuz a 0.7 cast spell does the same damage of a 1.1 cast spell in a dps rotation ..cuz the global cd doesnt go lower than 1.1 sec...(exactly it should be 1.0 sec but we take that at least u loose o.1 sec between a cast and the next one because of the lag, the lateny and fps's).
second: hit is important for a sp because of the most efficient "damage x second" spells has cooldown..i'm talking about swd and mindblast... so if u are a mage and u miss a frostfireball u can cast another one but if u are a sp is different cuz u miss a swd that does an hight coefficient of pure "damage per second" u have to w8 15 secs to do the next one.
finally crit: as more u have the better will be...that's the best stat to stack for you when u have hit capped and about 400-450 haste unbuffed (that's around a 13-14% cast reduction unbuffed that means u'll cast mindflayin in about 1.7..)