I ran into a conversation with someone who wanted to tank but only spends time on PvP.
Now, first of all I have to say that it's a horrible idea to tank without tanking. Gear will never replace knowledge.
Still, let's assume that you do indeed know how to tank, but you spent the last half a year doing nothing but PvP. Now you need to get into shape to take up that tanking again.
Your gear will, correctly, get you kicked out of every pug you join, so there has to be a way to get around it.
Well, there is. At least to get you into heroics, and from there you get valor points without destroying your supply of the conquest points you need to continue PvP.
Buy the season 10 helmet, cloak (or do the Thrall quest chain if you haven't done it) and belt. Get a season nine onehander. Continue doing PvP, but concentrate on getting honor. 375 honor buys you 250 justice points. You should be able to buy one JP piece or two daíly this way.
Do the Molten Front quests. The quick and dirty version is only doing only one day's worth of quests. That's enough to get you a necklace and boots.
You should be good for running the old Cata heroics within a week as tank, and from there on you have 490 valor points available per week. Gearing for the trolls would require the standard grind, and that's better explained in my failsafe gearing guide.