Skarner stun delay [GAMEPLAY]

At first I thought i was seeing things or i had a lag delay, but I was hitting my E with skarner and then when i hit them to activate the stun, they would get another hit off on me, sometimes killing me with that last hit. It became very obvious to me while playing against a tristana. Land the E, go to hit her, she would rocket jump away and get stunned when she landed. Skarner seems to be on a slight delay not in his favor.