Another reason to support my suggestion of reduced aim time and an increased reload time for Shreks.
I don't know where you got this aim time fixation from, but shrecks already fire pretty fast, what you are suggesting (longer reload times) would actually be a nerf to shrecks: the 99% of the time you will be chasing down a tank waiting for them to reload hoping to be able to fire another round before you have to retreat due to enemy reinforcements coming or the tank itself killing you.
no sane player will stay nowhere near the shrecks waiting for you to pop in and out of LoS