The Zandalari are traditionally friendly..enough... towards outsiders. Friendly perhaps isn't the right word. Smart enough not to be dicks for the sake of muh xenophobia, perhaps.
In Vanilla we met them in Yojamba Isle in Stranglethorn and we assist them with culling the Hakkari. You could even get exalted with them!
Next, we see them in Wrath in Zul'drak, documenting the downfall of the Drakkari. The Zandalari essentially establish themselves as #NotAllTrolls, rarely speak with that written accent we're used to, and are interested in preserving the history of their species as a method to show what *not* to do as a troll empire.
And then suddenly they go down the d-bag path in Cataclysm and try to rally the splintered troll empires instead of learning from the history they've been so keen on. They continue this trend in MoP.
What is revealed in MoP, however, is that the Zandalari are sort of split in two. The original emperor of the Zandalari, Rastakhan, is likely responsible for our first two interactions with the Zandalari, and a religious usurper/troll purist known as Zul is responsible for the dickery we experienced in Cata and MoP. Consider it perhaps two political parties and their affiliates. Rastakhan isn't about troll supremacy (at least not actively) and is open to working with other races, whereas Zul and his followers want to establish strict dominance over the "lesser races."
In the chronicles it sort of establishes the Zandalari as pricks, but only insofaras they don't trust their Mogu friends and are willing to backstab them at a moments notice. Of course, the Mogu feel the exact same way, and it isn't like the Horde already has tension in a similar fashion with the Forsaken. The Zandalari are indifferent towards the enslaved Pandaren and I suppose it could be argued they don't really get a say in the Mogu's affairs so why bother saying something and risking their alliance. I'm sure it is more of a "whatever none of my business and who really cares about these random panda people" sort of deal. It will be interesting to see (if we see at all) how the Pandaren feel about being allied with the Zandalari.
It has been said since that there is an on-going civil war between Zul's rebels and Rastakhan's loyalists. I can bet it will be discovered that Zul is in league with the blood trolls and whatever is corrupting the loa. Hint: old gods.
I hope this helps, I'm a big fan of the trolls.