Please fix Kalista's Rend

Does it ever happen to anyone else where you're attacking 2 targets with Hurricane then you Rend as one of the targets you are attacking is not low enough for Rend to kill it so the stray spear that hit's it after you Rend makes it go on CD? Kind of like it double Rends without any meaning. Idk just kinda pisses me off sometimes. I think to fix this problem the cast time on Rend would have to be lowered.

Here is the bug https://www.youtube.com/watch?v=TJaoaAypJ3A Skip to 11:40

[zombie-brand-mindblown]