Why do I want to see Medivh in Warlords? More importantly, how could I get to see Medivh in Warlords? Well, there's several ways this could happen. First off, we'd have to ask ourselves which Medivh would we even get to see - if there's an alternate Draenor with an Iron Horde that wants to invade our Azeroth, then by definition there's an alternate Azeroth that's going without its usual serving of orc invasion. And on that Azeroth there should be a Medivh - the guy who in our timeline built the Dark Portal and shared with Gul'dan the secret to creating one. And that Medivh should still contain within him the essence of Sargeras, the great big baddie above all others, the guy who signs Kil'jaeden's checks.
So I'd like to see what that Medivh is up to. Is he wondering where that army of orcs he was expecting had gotten off to? It's possible that he simply has no idea what Kil'jaeden was up to - Medivh originally discovered Gul'dan while searching the universe for a means to destroy humanity, as he believed (thanks to the presence of Sargeras in his mind) that doing so would help him learn mystical knowledge more effectively. In our timeline, he found Gul'dan after the Horde had destroyed the draenei and conquered their world, and were now finding themselves in a world poisoned by the fel energies they'd unleashed to earn their victory.