Is This Normal?

I main poke mages for the most part; especially, but I found out that these guys counter assassins in low elo!

Well, maybe not "counter". but do extremely well! With the mage rework, there comes the new and improved tear, which lowers your mana costs. You are then given the ability to cs with abilities, as much as you want! This means that the enemy Zed will be wondering how you both have the same cs, even if you are under turret most of the laning phase! I often starve out these assassins so much, that they dont get a kill, until an ally gives them one!

My question is, is this possible to rely on in middle tier elo? What can the enemy do, which counters my little tactic? Any improved versions of this?

Thanks for anyone who responded, and goodluck on the rift! ^.^