IAS doesn't increase your rend damage or damage per ticks, but that does not mean you shouldn't be stacking IAS with a Skorn. In fact it's quite the opposite, get as much IAS gear as you can. IAS is very important to a Skorn user and you should be aiming to get to around 1.3 APS at least to make the weapon viable. Also whatever you do, do NOT get rid of your IK belt. You do not have a LS Skorn and you need as much LS as you can get.
Sorry but pretty much ignore almost everything posted above by Zubenelakrab.
As for your next upgrade, you are a little short on crit chance. I would suggest looking for Lacuni's with CC but you cannot afford to really drop too much AR at your damage level since you aren't getting as much return from LS to compensate for it. So look for Lacunis with just AR and CC don't worry too much about getting STR on them. Your HP at 36k is also rather low, you should be able to get some Inna's pants with higher vit relatively cheap or at the very least replace some of your strength gems with vitality gems to compensate.
Your build also needs some work as it's really not optimized for, well anything. Switch runes for WoTB to Thrive on Chaose, drop leap for sprint with run like the wind for mobility. And with a Skorn if you're not using HoTA, I'm sorry but you're just doing it wrong. Drop over power for HoTA.
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