I agree with what you said about Greed, but all the mana regen is taken up. It's basically a spare point that you have in utility, and I decided I'd prefer 180 extra gold over a little extra mana, but it's entirely up to the user. As for being a glass cannon, that is true, but you should never really be in range of people, and should USUALLY be able to escape any gank. The extra defensive item early on is only necessary under certain conditions, such as if their team has VERY heavy CC/Chase ability, or you are dying often otherwise.

As for teleport, I dont think there are many better options. It's great for that early game mid lane control, which is probably where you are at you're weakest, and it retains its use mid game and late game also. The low CD flash iis just another reason not to get flash. I suppose Exhaust or Ignite are viable choices, but I have had too much success with teleport to advise people otherwise.

Thanks for the comments guys!

Solid Kass build although I don't like the mastery Greed as it is fairly useless, it gives 6 gold a minute so in a 30 minute game you will make 180 giold... Great thats going to buy you a few poitions. I would rather spend it in a bit more mana regen. Also your a glass cannon until you buy banshee's veil, I would advise getting a catalyst stone or something slightly defencive after your boots, you can always sell it later. Other than that I would say it is a strong build and guide.

Decent guide and build, but I can't say I agree with teleport, especially when you have a low cooldown flash at your disposal