Overall, your guide is decent, but there are a few major problems I have with your guide (and the way that you are telling us to play Malz).
1: you are constantly talking about his high cooldowns, and yet you never grab any CDR with him (other than blue buff). CDR is vital on malz, as it allows him to have the damage output needed to be a real constant threat.
2: you are talking about his low mana capabilities, but you never once get mana regen other than the blue buff.

Now, my biggest problem here is you complete and utter dependence on blue buff. As you put it: "[You] ALWAYS have a blue buff on". Relying so wholly on blue buff can cripple you and your team. When you start playing against more skilled opponents, and have junglers on your team, you CANNOT rely on blue buff to always be yours if ever. Your jungler will always have priority on buffs over you, and you simply grabbing blue buff whenever it is up, can lead to the enemy team getting fed. (a good team WILL ward buffs and will gank you there whenever they can)

3. Now, as much as I agree that the bonus health you are grabbing from Rylai's Crystal Scepter and Rod of Ages, this simply does not give malzahar the survivability he needs. With your high cooldowns and an ult that disables you, you will get focused down hard during any team fight. (not counting the aggro you pull just by owning a Mejai's Soulstealer) Something like Will of the Ancients will give you the staying power you need.
sorry, but -1