i dont think you'd benefit much on soul's attendant. just replace it with whitesun's passage. also, i recommend you to sideboard kor firewalker. he's good against red, of course =p
Do not forget Luminarch Ascension. Poison counters will not stop it from adding a counter, although you have to make sure to survive before you hit your 0 poison counters mark.
picture you self playing versus a WW quest deck. There is no way to counter Quest and eveb if you've leaked their weenies, it would still count in Quest counter.
Dread statuary.
I would add Into the Roil if I were you.
if i am not mistaken, ulamogs and erakul won't get exiled when u use nihil spellbomb... you cannot sac it in response to an emrakul being reshuffled.
memoricide and sadistic sac is a must in a mill deck. it shouldn't be a sideboard.
wurmcoil
angelic arbiter
Liquimetal + Splinter Twin on Manic Vandal or Oxidda Scrapmelter is a great combo,
Grindclock isn't needed and like what RPGsr4me said, Galvanic Blast isn't needed. I would rather put Pyromanscers Ascencion or Lightning Bolt
If the effect will be permanent then white can at least have a decent Removal again =)