Best advice I could give you is to not play any other than boomkin/dk/healer or Shadowcleave.
Let me begin with telling you the flaws of PHD. Firstly after cataclysm, dks haven't got much things to actually control the game than just pumping damage which isn't necessarily needed for a hunter comp. Believe me, I've met hunter comps as PHD and the only thing I can do is sit on their hunter while my hunter and my healer are trying to cordinate their cds together hoping to survive. I don't really have anything than just asphyxiate (which isn't even enough) to support my team with, Rets, warriors and enhancement shamans got way more things to support their team additional to damage. The only way damage will be something worthy is when you meet spellcleaves but that can also depend on how good your opponents are.
Let's compare it with Shadowcleave alright? So basically let's say we meet a hunter comp and you're meeting KFC or Thugcleave, what it ONLY require for you to survive them is whenever they try to approach your resto shaman (which may be your weakest point, but if your resto shaman is smart he should survive easily) he can, if not stupid actually use demonic gateway whenever you tell him to. Why should it come from the dk? Because the dk can use death grip or asphyxiate if the warrior decides to heroic leap to get back on our resto shaman or the rogue vanishing and cloak of shadow (subterfuge needs nerf kkthxbb). Additional to the beginning where it's all about going defensive, after that you can go on whoever you want except for the healer as shadowcleave against hunter comps. Later you'll see how they die like flies. Why you may ask? Cause you can damage them hard (cause of dots obviously) at the same time as you peel off your teammates. And against spellcleaves it's all depending on how good your team is.
And then dk/boomkin/healer which isn't directly effective as shadowcleave but it is handy, however the skillcap is high and your boomkin teammate is required not to be a LSD 2.0 hero (<----Very important). It's all about turtling, since the boomkin's offheals and CCs are compensations to the demonic gateway.
So a quick summary of Shadowcleave and dk/boomkin/healer:
- Your teammates are required not to be dumb
- Your teammates needs to understand common sense
- Your warlock at some circumstances needs to be able to dmg even if he is getting focused. Pretty much a l2p issue, I've had loads of warlock partners who pretty much do nothing if they get focused.
- Boomkin requires to be smart and actually know how to use his defensives properly.
Oh and I also forgot about how to beat mage/warr as shadowcleave. Well, peel off your rshaman during the whole game and stop the warr, otherwise if they go on you or the warlock. Consider it as a free win.
Same goes for boomkin/dk/healer but except that if they go on your rshaman or boomkin, you're screwed.
I only see shadowcleave or dk/boomkin/healer as the optional comps for high ratings. I'm not saying PHD is bad but you'll have to be really lucky with who you're meeting.