Garrosh had done many things as Warchief of the Horde.
He has polluted rivers, destroyed cities and lead conquests of areas once peaceful.
He has also brought wealth, safety and a new lease on life for those who follow his Ideals.
Clearly, he is not working though, he opresses opinions that are not his own, he is wasteful, brutish and hateful.
But is an Aggresive Horde, an Active Horde, a Bad thing?
Sitting in the desert did the Orcs nothing, it watched them slowly die away and their proud culture stagnate.
Another Thrall would be worse than Garrosh, a symbol of subservience for the Horde not to look up to, but to feel looked down Upon.
The Horde is a united faction of Outcasts, united by a purpose to be strong together and protected together. The Horde is Family, and Family should look out for it's own first.