I see what you are trying to do but if you want to mill your opponent you have to make it quick, otherwise they will rush you down. Mill and Drill (SUPER BUDGET) Is an example of a great low cost combo which mills your opponent. My cousin and I also designed an Artifact mill combo between Krark-Clan Ironworks + Grinding Station and 2 Myr Retriever. He also did a deck which used Pili-Pala and Grand Architect with some "Pay X and opponent puts X cards from library to graveyard".

If you are willing to go all out without a budget restriction am sure there are some other combos which might be a bit more expensive moneywise but are much more efficient mechanicwise.

Why surgical over extirpate?

Having the flexibility of makes it more desirable. Especially if I need to hit an Emrakul, the Aeons Torn after casting multiple mill spells

Have you thought of adding Mission Briefing and Shelldock Isle