Thanks for the feedback on the guide!
I see the value of a philosopher's stone. I can see a game where the trade-off could be made by the player. On the one hand we get extra HP regen, along with bonus income, which Heimer loves. With the chalice, we are focusing more on boosting up some of that starter MResist, helping early game survivability. I will outline this better in the guide as I get ready to do an update!
The Fiendish Codex is the perfect item - but I feel it is much more geared toward AP Heimer, especially with the 9/0/21 build. It will help him reach the cap (39% or so I think, close) more quickly, and cheaply - while giving him AP and mana regen to start. It builds nicely of the Meki Pendant.
However, I feel the build I have essentially outlined favors survivability much more. Looking it over more closely, I think the ideal masteries would be 0/21/9 for this Heimer. By the same token, the shroud will fully fill him up to the 40% cooldown reduction, without necessarily breaking the bank (mid-game), and this is without the need for any masteries lowering cooldown at all. In fact, the extra CD reduction from the heart is un-needed, but following the theme of the build, I feel the additional armor and reduced enemy attack speed help him greatly.
Without disagreeing much at all, I think this build lends itself to the shroud and heart, as they give him mana, armor, and the CD reduction that he needs. Masteries can be spent on furthering the defensive abilities, with some in utility for mana control.
Again, thanks and keep leaving feedback/ideas!