@FanOfMostEverything  
Your opponent does chose what they have to sacrifice but I totally agree. I have a special hate for eldrazi so I personally think that any card with that ability should be around cmc 20 and have a Phage clause. Buuuut yes, if you replace bloodthirst with annihilator on this card I would also change the cost to 6RB.

The use of bloodthirst is understandable, given how black did get it in M12. If this weren’t explicitly a Ravnica card, I’d be fine with it.
 
Also, do not underestimate the power of double strike. Even without the bloodthirst, this is effectively a 4/2 hasty creature that needs at least 3 toughness in its way to have any hope of killing it… though that actually raises another issue. Combat damage is the most common way to enable bloodthirst, which means that bloodthirst and haste on the same creature don’t mix all that well. Take the suggestions of both commenters before me: Make her a 3BR with unleash where you currently have bloodthirst (which means you can just simplify that last line to “Other creatures you control have unleash.”) and you’ll be golden.
 
@broniepheus  
Annihilator? As in the Eldrazi “everything that gets close dies” ability? That shouldn’t go on anything that costs less than eight.

@Bardic_Knowledge  
@broniepheus  
To be honest, I had forgotten that Bloodthirst came from Gruul. When I was building the card I was trying to have a card that would have some level of synergy with other Rakdos cards. I will try harder next time.

Why bloodthirst when annihilator and unleash are just as “in flavor” without messing up the color pie?

Well, there’s one thing that pops up immediately: Bloodthirst is a Gruul keyword, not Rakdos. Otherwise, the biggest issue is that a four CMC feels a little undercosted. I’d make it 3BR.