Diplomatic immunity really isn't good enough. For any MTG deck. Ever.
What is the 2 swamps for? 1 should be sufficient for all intents and purposes in a mana drain based deck.
Why death wish? Dosn't really seem optimal.
Here's a deck list i've been toying around with, although i haven't really tested in a while:
Mana: (24)
2 Underground sea
2 Volcanic island
2 Tundra
5 Fetch
1 Island
2 Wasteland
1 Strip mine
1 LoA
1 Tolarian academy
7 Solomoxen
Disruption: (15)
4 Force of will
4 Mana drain
4 Mana leak
3 Disrupt
Draw/Search: (11)
4 Brainstorm
2 Skeletal scrying
1 Ancestral recall
1 Fact or fiction
1 Mystical tutor
1 Vampiric tutor
1 Demonic tutor
Broken: (4)
1 Yawgmoth's will
1 Time walk
1 Tinker
1 Balance
Utility: (6)
2 Gorilla shaman
2 Cunning wish
1 Platinum angel/Darksteel collosus/Sundering titan (I used Platinum angel)
1 Crucible of worlds
Sideboard: (15)
3 Red Blasts
2 Swords to plowshares
1 Echoing truth
1 Skeletal scrying
2 Rack and ruin
2 Massacre/Pyroclasm
4 Chalice of the void
The deck plays out like draw, go for the first turns, and then it locks the opponent out with mana denial or just more counterspell...Or a combination.
I think it would do better then your deck, although it's primary focus isn't on the angel.
/Zeus
If the entire point of the deck is to tinker up a big robot why not include personal tutor too?
It's not the worst keeper style deck ever, just nothing revolutionary.
p.s.
You absolutely need leylines in the board or you'll get rolled by flash. I might even consider adding leyline of singularity too since it's pretty good right now with all the empty the warrens tokens floating around.