hey man, an easy way for me to make suggestions here is to point you towards my grixis EDH deck Blinking, Unearthed Frenzy, full of grixis good stuff and its a reanimator deck, you may want to change your general to Sedris, the Traitor King he.....is....SICK for reanimation bro!! :-) anyways take a look and then if you ask for help on a specific combo or card or strategy I will be happy to give mroe specific help mate :-)

You might want to increase the land count to about 36; 31 is low for an EDH deck.

What's your budget for this deck?

I do agree about increasing the land count. You can suggest any cards that would be useful. Just because it's out of my budget now doesn't mean that I might not be able to acquire one later.

Consider the following cards:

Cascade Bluffs

Graven Cairns

Sunken Ruins

Sulfurous Springs

Underground River

Shivan Reef

card:Volrath's Stronghold

Reflecting Pool

Rhystic Study

Necropotence

Phyrexian Arena

Stranglehold

Sol Ring

Thran Dynamo

Gilded Lotus

Chromatic Lantern

Except for Necropotence all your suggestions are good. Except for the 10th edition pain lands, I already own all the other cards, but they are in other decks. 'Potence is out because I need to be able to discard into my graveyard to reanimate. Was my deck's only weak point its mana base?

No; some of the other cards could be improved. For example, card:Geralf's Mindcrusher, Chill of Foreboding , and similar cards are kind of underwhelming. It would be better to have spells that let you pick what card(s) you're dumping into your graveyard.

Also, burn spells like Lightning Bolt are pretty bad in EDH.

You may want to read this article for more of my philosophy on what belongs in an EDH deck and what is subpar.

Which cards am I missing that let me put selected cards in my graveyard?

Corpse Connoisseur is one.

The general idea I'm getting at is that indiscriminate mill, especially small-scale indiscriminate mill, is pretty ineffective. You'll be wasting your resources trying to put creature cards into your graveyard and likely end up putting plenty of otherwise useful cards into the yard with them.