Here's Voljin's Ally relevant dialog. I know some of this has been posted elsewhere, but I'm a little short of time to dig out and check screenshots, so here it is...Vol'jin (Ally)
After a brief meeting w Amber and Sully, you do a quest in which you: Find some Kor'kron documents and then free Zen'tabra from a cage. She then escapes w/o further help from you. You go back to Sully and Amber and suggest that you go to Vol'jin and offer to help him to futher ally interests. You go to Vol'jins new camp (Razor Hill Watchtower), which is now a (small) sanctuary zone. Vol'jin dialog header:
<The stench around Vol'jin's makeshift camp is intolerable. The troll leader allows you to speak first, while his guards eye you warily.>Vol'jin quest: Vol'jin of the Darkspear (Finish)
<The troll does not have strong grasp of the common tongue, and his throat is still bandaged from a knife wound. But the meaning of his words is clear.>Vol'jin Optional Dialog 1:
What de Alliance want wit' ol Vol'jin, Hmm? Zen'tabra says we got a common enemy. That don't make us friends.
But... Maybe we can work together dis once. You want to strangle de Warchief, hm? Shut 'im out?
<Vol'jin smiles disarmingly, his grin slow and savage.>
Question: Why are the Darkspear in rebellion against Garrosh?Vol'jin Optional Dialog 2:
<Vol'jin twists his face into a scowl.>
Yoi wouldn't understand. What's de Horde ta ya, human? Hm? Diseased? Alien? Betrayers? Demon-blooded? Beasts? I know what ya say 'bout us.
I'll tell ya what de Horde is. De Horde dat me an' Thrall built. It be a family. When de whole world try to put us down, de family come an' pick us back up.
Hellscream, he don't see family. Ain't never had one.
Question: What about Hellscream? What does the Horde mean to him?
For him, Horde be about orcs, an' buildin' up orc power. Like he just come through de portal. Anyone stand in his way, anyone tink diff'rent, he shut 'em up.
<Vol'jin runs his three-fingered hand across his scar.>
He like an angry dog. Oh, I fight next to Hellscream in battle, sure. But put him in charge? Ya askin' for trouble. He pick his favorites, start this war, shove bruddahs aside... He don't tink he need nobody else. Well, he wrong.
He gonna learn: ya never cross family.
Question: Why should we help you? What if we kept the Barrens supplies for ourselves?
<Vol'jin cackles, the stench of his hot breath reeking in your nostrils.>
Oh, ya got annudda plan? I got anudda plan, too. I let ya siege Orgrimmar on ya own. See how far ya get. An' once da city be filled wit' corpses, den me shadow hunters come in, we mop up what left, kill Kor'kron an' Alliance alike. Give ya dead ta Sylvanas. Hmm! I save a lot a Darkspear lives wit' dis plan!
Mmnn? You don't like? Then we stay wit' da first plan. We work together.
We don't even have ta like each other.
New reply to the above added to PTR 4/18...
Vol'jin Quest: Battlefield: Barrens
Question: [Call his bluff] Why don't WE wait until YOU attack Orgrimmar, and then mop up YOUR dead?
<Vol'jin sees his opportunity slipping away. He holds up his hands.>
Wait now, human! Orgrimmar be a fortress. My people, we ain't gonna crack dat nut on our own. How long we gonna last out here? Days? Weeks? Vol'jin can't say.
You keep da supplies commin', an' I promise, more Kor'kron gonna die. Before ya troops even land! The blood bein' spilt ain't even ya own! Surely dat be worth a few crates of meat?
Ya want we work together on dis, ya gotta earn me trust.
In Northern Barrens, de Ko'kron be massin' for war. Hellscream's goons be stockpilin' lumber, oil, stone, an' meat. Supplies de Darkspear want ta use against 'im.
Go to de Barrens, Kill de Kor'kron. Bring me dem supplies! Fight dem whereever dey srping up, escort supply caravans, group up to take down de dangerous ones. Whatever ya gotta do.
Prove ta me da Alliance wants dis! I be watchin'.
Finish (after collecting stone, meat and oil for the Darkspear):
<Vol'jin motions to his guards to allow you to come forward and speak.>
De Barrens be splattered wit' blood, human. Ya done right by me.
Tell de Alliance ta rally its fleet. When de time comes, de Darkspear an' de other rebels will try ta hold de harbor for ya. Hellscream made too many enemies ta fight 'em all off at once, hah!
<The troll's face becomes deadly serious.>
Ya have me thanks, human. Dis rebellion only gonna get so far wit'out ya.
Vol'jin: Very well. Ya earned me trust. I will put me faith in tha Alliance to do tha right ting.
Vol'jin: The Darkspear and her allies will attack orgrimmar by land, so that you can attack her by sea. It be the only way.
Completing this earns Darkspear Revolutionary title plus the letter from Varian.
Update 4/18. Now you won't get the achievement/title until you complete a subsequent (non-Vol'jin) quest.) Also title is now 'the Hordebreaker'.Further Notes:
There's a Darkspear Rebellion Quartermaster, but there is no faction reputation associated with it. Quartermaster items are not dependent on (non-existent) rank but only on northern barrens loot (stone, lumber, meat, oil). There's a weekly quest for an additional special item, which is used in conjunction w the zones drops/faction rewards.
From Vol'jin comment plus Varian's letter, it appears the next major event is Alliance landing at Bloodfist Bay (the docks just to the SE of Orgimmar where the goblin ship landed). I don't know when that would happen. My guess would be later in 5.3, since 5.3 looks so think questwise right now. But perhaps it won't happen until 5.4.
Amber and Sully are only present for the initial arrival quests. Once you head off to Vol'jin, they're gone. Ally's zone work at this point will be exactly the same as the Hordes -- messing around in Northern Barrens, attacking Kor'kron outposts and commanders and escorting caravans -- and then turning the supplies over to the Darkspear.