From this prompt on the Warcraft Kinkmeme: Malfurion makes a point of 'visiting' every leader of the Horde at least once a year to maintain this neutrality. He goes for a roll in the forest with Sylvanas, ruts with Cairne, and later Baine, drunkenly fumbles with Vol'jin, has a foursome with Lor'themar and his co-rulers, and used to spend a steamy night with Thrall.
When Garrosh becomes Warchief, nobody thinks to inform him of this tradition, so he's rather confused when Malfurion drops in and is giving him the old suggestive eyebrow waggle. He comes around about the same time as when he comes as it turns out age brings phenomenal experience.
Malfurion had his own allegences. He knew that he was often though of only when accompanying Tyrande, and was proud of that. The High Priestess; his love, who led their people bravely and with determination. But the Arch-druid was not a political leader; The Cenarion Circle worked for the betterment and healing of the entire world , and that meant not only maintaining strong ties to the Alliance but to the Horde as well.
If his approach to ensuring this was a bit novel, well, no one could say it didn't get results.
Cairn Bloodhoof had been a dear friend; and while his son Baine was a grown Tauren, Malfurion found himself offering comfort that was more emotional than physical. Perhaps in the future, but he was quite happy to support the young chieftain until he decided to take him up on the offer.
Vol'jin was a mystery; cunning and fierce, and while Malfurion always tried to unravel it the troll outsmarted his attempts. One drink becoming three becoming five; until he woke the next morning smelling like smoke, with sore muscles he'd feel for days. Even if he didn't remember exactly how he'd gotten them.
Lor'themar Theron was at once both the most difficult and most pleasant to be acquainted with. One the one hand the Sin'dorei leader was the epitome of charm, as well as being quite passionate about gardening and forestry; something Malfurion himself could spend hours discussing. On the other hand, it had taken a few visits to become comfortable with the idea that the Regent's advisers adamantly refused to allow them to be alone together. When Lor'themar had finally decided on compromising for the best results Malfurion hadn't expected them to join in, but he found it very difficult to complain.
Sylvanas was a huntress at heart, and even undeath had been unable change that. Malfurion ran as an elk and flew as a hawk and stalked as a great cat; but when she caught him, he didn't put up anything but token struggles.
Garrosh was young, he understood, untried as a leader yet meant to fill Thrall's place with honor. Malfurion supposed he shouldn't have been surprised at the young Warchief's surprise when he appeared and asked for a private audience. Later—after the third time he had explained why he was there, and promising again that he meant no harm, and really if Garrosh wanted to confirm his intentions with Thrall he could come back some other time—he set about showing the orc why there were a few more perks to this whole arrangement than just maintaining his neutrality.
Notes: Hehe, Mal kind of comes off as a bit if a lech in this, and forgive the lack of anything graphic. I just really like the idea of Garrosh's reaction and the dynamic Mal would have with each faction leader.