I did some testing and I finally found out the reason why Jakiro is so powerful in dota2.
In dota2, if you target a unit rather on the ground, during the 0.65 seconds cast animation, Jakiro will lock onto his target (will turn and follow the targeted unit), so in the end the enemy has only 0.4 seconds to dodge 150 width of his stun.
But in dota1, Ice path will not turn after the targeted unit during his cast animation. Ice Path will go off on the location where you clicked despite being on a unit or ground (ignores unit targeting). This is why his Ice path in dota2 turned into a guaranteed stun that is almost impossible to evade.