I have found an interesting list of a Rakdos midrange deck while browsing through the Standard decklists at MtgTop8.com. The card choices are somewhat between that of Mono Red aggro and a Rakdos control deck. The new Theros cards added were Tymaret, Purphoros and Stormbreathe Dragon. A cool shenanigan in the deck is the playset of Molten Birth, which can be used for Tyramet’s damage ability and that of Purphoros’ damage trigger.

Here is the list:

Maindeck
10 Mountain
4 Swamp
4 Blood Crypt
4 Rakdos Guildgate

4 Young Pyromancer
4 Tymaret, the Murder King
3 Chandra’s Phoenix
3 Purphoros, God of the Forge
2 Stormbreath Dragon

4 Molten Birth
4 Magma Jet
4 Shock
4 Lightning Strike
3 Dreadbore
3 Chandra, Pyromaster

Sideboard
1 Dreadbore
3 Skullcrack
3 Thoughtseize
2 Rakdos Charm
3 Mizzium Mortars
3 Hero’s Downfall

Source: http://mtgtop8.com/event?e=5725&d=233194