My Ideas on How to Fix the 4 Reworks (At least a little)
So, Skarner's rework is the first one that should probably be talked about. If he were to even just get the movement speed back on his Q, he would be in a good place. So, if that could be added back, and maybe the Q cooldown going down by a little bit more than .25, while perhaps nerfing down the spire bonuses to balance it.
For Darius, if the bloodrage AD was to be lowered by even half, it would still be good, and maybe just give him a bit more movement speed now that his Q depends on his positioning/movement more than it previously did. Also, if the delay on his Q could be just a tad shorter, it would help with precision and also still keep the feeling of a massive axe being swung around. This would also help him outside of lane as well.
For Garen, if his W passive were to return to being percentage resistances, and make his E slow a bit less substantial, so that he can still keep up with people. Maybe 5%, that way he can't constantly keep up with you, yet he isn't left behind in the dust. I feel that would help him to make better use of his new-found true damage, and also help him remain the lane bully he's meant to be.
For Mordekaiser...I'm borderline lost. He's so awkward that it's too hard for me to even try and figure out a fix.