User blog comment:RoznosicielCiast/Is Siphoning Strike too strong?/@comment-11623843-20131105020113

You forgot about one thing: mobility. You assumed that nasus will be able to easily Q the carry multple times in a fight. To do this, you have 1 long cooldown CC ability that you'll use on the carry. This stops them from running, but it doesn't stop their team from peeling for them. CC onto you will stop you from reaching the carry if you dive right into the fight. Even if you manage a couple Qs, you need 4-5 to kill anyone, and the carry has lifesteal. This takes ~15 seconds to get, during which time they can make you very, very dead. Tank Nasus also has not much damage besides his Q. As the tank, you can manage to bait their CC and get them to focus you, but you don't have much CC or damage like some tanks or fighters.