[Senna]

It normally carries different counter players such as damage over time (If you're faster, it becomes useless if you apply DoT on the target), the shades that can be used against them with vampire weapons, spirit jar any so on. I can see it getting annoying if the person only uses that every turn however. A 2 round CD works well but nothing would be stopping the person from just running across the entire map at that point then use it again after.

It falls under a abusive Kite strats. Probly lessen the spread range with a 2 round CD would be good.