Hello,
For one, check if your fightclass use all spells required and if optimised.
If your fightclass is good but slow, you can:
Activate options (in advanced general settings) "Unlock fps limit" and "Improve combat rotation speed".
In the fightclass settings you can also increment "Frame per seconde".
(More you have fps in wow, more wrobot is reactive, use low image quality in wow to get the best fps).