The haste softcap is when GCD is 1 second. After that haste is still good for an enhancement shaman, but not as good as it was before.
You should always be exp capped, or close too. Just stick to the exp cap, you don't have ver ygood gear anyway so you are not raiding end game (where, theoretically, a massive amount of theorycrafting could show you that dropping 2 exp for haste is good) so you do not need to min/max that much since your gear changes so much anyway. Not saying that you should not make an effort, just that the dps gain is so minimal that it's really nothing to worry about.