You absolutely have to max Malefic Visions 1st and ist a liitle boring to read this, use BB-coding, give and some color and put a few pictures and mvies in it.

Stopped reading at "I haven't made this guide for farming minions" Yes maxing call of the void will give you a tiny bit more burst in a 1 v 1 but malefic visions can equally farm an entire minion wave, maybe two, in one cast. It also will replenish your entire mana bar if it clears a few waves on one cast. It can also be used for mana-cheaper harass on the opponent that they can't dodge (Unlike CotV). Farming minions is a much more reliable and almost always better source of income than constantly trying to kill enemy champs. Which in turn allows you to buy better items and that in turn makes that malefic visions (and every other spell) do a ton more.
TL;DR If your build is focused completely on champ killing and not on minion farming, it fails.

there is a reason as to why i dont max malefic visions first, Demon Cleaner. It is primarily because i have a BURST castor setup and you'll be surprised how fast your opponent's health bar will get depleted with Call of the Void rather than the damage over time with malefic visions. I understand that malefic visions IS good for farming but i haven't made this guide for farming minions, i made it so that you can burst down your laning opponent. Also i havent maxed out malefic visions as call of the void has far more range than it :) plus you get more gold for champion kills and a maxed out and nicely aimed call of the void can take out a minion wave in just a second :D

As for your concern Asustador, it is VERY easy to burst down other mages as they are either very fragile and i can use my standard spell combo or if they're tanky like vladimir, i can use Null Zone. I did not make this guide without thinking about it first, and i'd appreciate it if you would consider that :) Also I see that you have made a valid point and i will edit my team fight section a bit, hope you see this! :D

I think he think that hourglass will give him all survivability he needs,and 1on1 other casters he can win...Kinda bad idea no hp items so you will be focused and killed in few hits,dont wanna downvote just i think you need considerate it

Farm with Malefic Visions, not by lasthitting and.. don't you think that you are a BIT squishy? and btw, who sends something else than a apcarry mid?
btw: Malefic Visions is THE skill. max it up first.