Mage arcane

I don't know if it will be the best place to put it.
I have a mage in the Icecrown realm, her talent specialization is arcane in PVE and frost in PVP. In arcane, I have geared to have 1000 haste but I have realized that the cast time of an arcane explosion is the same as when it had 700 haste. I have changed the gems again to put everything to spell power and now I have less haste and the cast time is the same as when I had more haste.
If you can help me I would appreciate it.
My magician is https://armory.warmane.com/character/Arethell/Icecrown in case you want to see if there is something wrong .
Thanks in advance

Fire is better