We know that the Mantid are related to the Aqir, and may even be an offshoot of the Aqir. We know they served an Old God, much like the Qiraji worshiped C'Thun, and the Nerubians worshiped Yogg-Saron. However, the Mantid turned out to be different than the others with their priest class, the Klaxxi. They would decide how the empire would be ruled, even more than each empress throughout history. They wanted to take down Empress Shek'zeer due to the fact she had allied with the Sha, despite the fact that the Klaxxi stated they would ally with Y'Shaarj again if he were to come back.
With the inclusion of the Paragons in Siege of Orgrimmar, it would seem they have allied with Garrosh since he holds the physical embodiment of Y'Shaarj - his heart. This solidifed the reason why the Mantid would swarm Pandaria (more than world domination) since it would appear they were trying to get to the Vale to get the Heart for themselves. Why, then, would they oppose the Sha if they are the shadows of the Old God? Why did they feel the need to take down Shek'zeer when she was doing what the Klaxxi are doing in 5.4?
To me, the Mantid are wrapped in mystery that I must uncover. We know they are similar to other Aqir-descended races, but we don't precisely know if they are related directly. They called Ahn'Qiraj and Azjol-Nerub their "sister kingdoms" but they never outright stated they are another "breed" of Aqir. We never even learned the name of the Mantid empire fully, since their empire spans across the Dread Wastes and Townlong Steppes.
What are your speculations? Are they related to the Aqir? Were the actions of the Klaxxi justified in patch 5.0? Are they justified in 5.4?