you must stand still to cast pot/rune on rl tibia, u cant do it while running. So therefor, when u get paralyzed and you're moving from sqm x to y, you will get exhaust because you are not standing still your are "running". Also paralyzes on real tibia makes you more slowed then on moonhawk, thats a difference too.
To make myself clear, if you are running and you get paralyzed, you will actually not be exhausted. But the spells you cast will only effect when u get to the next sqm properly. That walking time is your exhaust, u cant say 1 sec or 2, if u are lower lvl then it will take more. If you sidestep, which is supposed to be slowest step u can take, you will be "exhausted" as hell.
To start with, make paralyzes stronger. So they make you slower, slower then it is atm. Also do something about dash somehow, people are not supposed to be this fast while sidestepping or running.