- Liliana's Caress is strictly better than Megrim, should maximize that.
- Lots of targetted creature control, which is great if you're playing against a deck with a bunch of creatures, but not so hot otherwise.  Too much targeted removal, but not enough mass removal.
- You have lots of mana acceleration, but nothing that really needs it.  The most expensive card in your deck you should be able to play by turn three, so you really don't need any of the mana acceleration.
- Without an early Wheel of Fate, this deck will fizzle out in a hurry.  It needs more card drawing.
- Cabal Therapy is not an ideal card to use without having creatures to flash it back.  I'd add creatures before removing it, though.
 
Here is how I would build this deck (trying to keep cost down):
4 Lightning Bolt
4 Terminate
4 Wheel of Fate
3 Burning Inquiry
3 Cabal Therapy
4 Duress
3 Blightning
4 Liliana's Caress
2 Megrim
4 Phyrexian Rager
3 Ravenous Rats
8 Mountain
14 Swamp
 
This build isn't perfect - it still lacks mass removal (I'd use Damnation if you have it, maybe Crypt Rats, maybe Mutilate) and still doesn't have enough card draw (Substitute Dark Confidantfor Ragers, maybe Night's Whisper or Phyrexian Arena)