For Thralls insubordination? I mean, Garrosh isn't gonna sit tight when he finds out Thrall liberated the Echo Isles and killed Kor'Kron. However, he can't really challenge Thrall (yet), and even if he could, that would risk dividng the orcs. But Aggra? Im not sure many in Orgrimmar even know of her.
I mean the pregnancy seemed to be a big thing, but it seems she already had the child despite there being scene or even comment made about it. It's as is Blizz wanted to pop that baby out asap. Why? Cause it makes Aggra expendable.
Blizzard likes Thrall. Fans like Thrall, but hate Go'el. As long as Aggra exist, so to will Go'el. I think Blizz wants the badass Thrall that fans like back, but still want him to have a sense of his Shamanistic and family roots, hence his child.