Durotar had farms pre-Cata as well - such as the Rocktusk and Tok'ren Farms near the security of Ogrimmar's gates. Post-Cata Durotar now also has a watershed which it previously lacked, which may slowly but surely have an effect on the originally dry and hardscrabble terrain.
Gorgonna doesn't allude to it, but Thrall does in "The Shattering," saying that it was his hope that the Orcs would refine the land. Thrall seemed to feel as if the Orcs needed to find a kind of spiritual equilibrium with the land, that it and they were reflections of one another. Durotar suited the harsh nature of the Orcish soul as it was when he first brought them to Kalimdor, but the idea seemed to be that as the Orcs returned to their roots they would find their balance and the land itself would reflect that (with the blessing of both the ancestors and the Elemental spirits). We know that a powerful Wild spirit such as Aessina can spontaneously prompt wild growth of nature even in a land scarred by rampaging fire elementals, perhaps the Shamanic Spirit of the Wilds could've done similar to Durotar when the Orcs were ready to receive such a gift.
We know Saurfang was present at Warsong Hold in Cata because "The Shattering" features him there, and he doesn't return with Cairne and Garrosh back to Ogrimmar aboard their vessel as they leave. Saurfang had lost his son in the Northrend campaign and was basically retiring in Warsong Hold a broken and grieving man. He's out of focus for the entirety of Cata and the majority of MoP. It's the oath he made to Garrosh during the early days of WotLK that actually stirs him from torpor, as at Thrall's behest he leaves the Hold and travels to Orgrimmar to enact his promise to the younger Hellscream to end him if he started down the path of Grom. His role was minimal because he was an ocean away from the heart of the conflict, manning an essentially derelict fortification in his dotage. I doubt he was receiving intelligence reports from the Horde as it was busy tearing itself apart, and was probably largely unaware of what was happening (or honestly may not have cared given his mental state at the time).