For months I have carried extra gear for my 'Heroic' set, which dumped +hit for things like crit and SP. I used this and found a modest decrease in the amount of time heroics took to complete.

I even took this 1 step further, and said "Hey, raid trash is only level 82, too!" So I started wearing this set for trash as well.

But the realization came; that for the miniscule improvement I was observing was completely wiped out by that one time I didnt change back to my full hit gear, and only saw miss miss miss on my logs.

Maybe you'll have better luck than me, and your theories are accurate, but I failed when I tried to implement them.