Haven't tried the build out yet so im not gonna vote now but from the looks of it its kinda made for the unskilled ones who can't play veigar well enough and need him in tank form to be able to stay alive. its true that 700 AP suffice but seeing you got no increased mana early game i'm pretty sure you'll have to recall alot to refill it, leaving an opening every time for opponent team to strike. If you don't recall and stay without mana i'd say you won't even be a danger to your opponents cause you can only scratch them a bit with normal attacks while they finish you off slowly. My opinion is that a real veigar build starts with decent AP and enough mana from start. You could try out my own veigar guide but let me warn you that it requires at least a bit of skill to use it well.

This build is meant for off-tank, but I don't see how good it can be.

Frozen Heart? Anti-AD AP best choice is Zhonya. Admittingly Frozen Heart is useful, but the mana kinda sucks by the time you get it, CDR is probably not that needed, easily replaceable by Randuin's Omen, which costs less if you buy it part for part.

700 AP? Reachable? Without early game mana regen, until completed Phil stone. I'll rather get Faerie charm first for mana, or even getting meki 1st and getting phil next.

Warmog's? Even off tanks don't get warmogs that much. I'll rather go for RoA for AP and early game easier boost.

Event Horizon at level 6? Ult at level 8? Seriously, where do you CC someone before lvl 6? Where do you pwn before lvl 8?

I'm pretty sure its really easy to dodge a Dark Matter w/o CC. Which is why you have a stun. Take one level on it?

Health alone is not enough. You have weak MR. Fix that?

Hope it helps.

No Archangels, no Deathfire grasp, Q needs to be maxed out first. Kind of a weird build... I'll probably try this out in a bot game or something. I'm assuming you sell Meki Pendant and Philostone later?

Really weird build, not sure what to say.