Now, see, I really don't see that... It either forces a person to stand still (always a frightening prospect, and also one that destroys attempts at farming in lane), or it cripples about 90% of heroes by taking away their damaging, disabling, and escaping abilities. And if you use it in a chase, it will just about guarantee a kill either because it, again, takes away their ability to disable or escape; and once it's done with that it throws a decent-length full stun on the end of it. And if people don't like moving, you can make them. Just like Bloodseeker's ravage, you can push people around with the Force Staff in order to make them lose a chunk of mana. And since it's percentage based, it scales with the people you're using it against. And since it burns mana instead of health, the amount removed cannot be reduced.
At max level, one shot of Force Staff will instantly burn 30% of a character's max mana, if they remain completely still otherwise. And if they have less than 30% total, they will immediately be stunned for 2.2 seconds. Now, 2.2 seconds may not seem like much, but the important thing to recognize here is that they now have no mana. That means no blink, no Windrun, certainly no Ravage or Time Walk... Not even the usage of their own Blink Daggers or Force Staves... Hell, they won't even be able to use mana boots.