Miss Fortune's W

PASSIVE: Miss Fortune gains 25 bonus movement speed if she has not taken damage in the last 5 seconds, excluding periodic damage. This bonus is increased to a greater amount after another 5 seconds.

ACTIVE: Miss Fortune gains bonus attack speed for 4 seconds and brings Strut's passive effect to full power.

As a Miss Fortune main i feel that changes need to be made to the movement speed part of her W. It does feel very helpful when it the move speed bonus is active, but it is too far easy to deactivate it making her super immobile. Sure you can activate W to gain the maximum MS bonus again, but one tick of damage deactivates it again. I feel like building bloodthirster is a must to help make the passive somewhat better.

Perhaps give the passive a few seconds before it can be deactivated after using W or make the MS bonus immune to minion/monster damage.

What are your thoughts MF players?