That would be a viable point to make were his goals to have changed at any point, but that isn't really the case. What changed were his knowledge and circumstances. Garrosh's preoccupation at all times was with what benefitted the orcs and on a personal level to be the ideal orc. Even angsty Outland Garrosh was angsty because he was afraid to make any decisions as, on account of his connection to his father, any decision he did make might screw the orcs over. His entire grievances with the Alliance come down to what he saw of the state of the orcs under Thrall and it's what soured him on Thrall in general. His issues with fel also go back to his dad and the orcs at large and the specific qualities it has that make it non-viable for the interests of his people.
His stance on fel and void then is consistent on why he approves of one and not the other and doesn't constitute any kind of hypocrisy. The Mana Bomb is even more of a non-issue as it was never even implied to be outside his wheelhouse and the way the morality of the weapon is treated is barking considering both the completely legitimate target, its strategic use and who was actually in Theramore when it hit. Was Garrosh willing to compromise his stances to a point in order to achieve his objectives? Yes, he did send the undead en masse at Gilneas, but he plainly disapproved of both the Blight and necromancy, he just had no means of enforcing this without handicapping the war effort. Since the warlock thing with Garrosh'ar and Darkspear Isle, nonsense though it is, still canonically happened, we can attribute the same to them - he had them lying around, so he might as well use them. By Siege of Orgrimmar they no longer had any utility and amounted to a completely hostile internal element. Hell, the main warlock in Orgrimmar was a Legion cultist that Thrall kept around in order to keep track of his movements, so even disregarding his history and the nature of the magic itself, it's hardly a surprise that a very different kind of manager from Thrall might not consider keeping Neeru around worth the trouble.
The war effort at large was the driving interest of what he meant to accomplish to benefit the orcs. Garrosh did compromise on the undead and to a far lesser extent the fel, what with it being two solitary cases amidst a policy that was otherwise hostile, but the degrees to which he did so were less than his predecessors and peers when it came to their own supposed values. Unlike Thrall, he outlawed the Blight and implemented overseers with Sylvanas to ensure the war was waged in the way he wanted. Was it used anyway and his overseer subverted? Sure, but the effort was made. Compromises are part of leadership. Garrosh made far fewer of these compromises as regards his values than his predecessor and that's why I can't agree with your position. He was toppled after all in large part because he tried to apply those values on people who didn't care about them and to push his interests on states that didn't have much to gain from them. Also because of post-Tides of War collective amnesia, but anyway.