The big thing i really dislike about vsing current darius is his huge heal in lane. I think it needs to be reduced even further than it currently is slated for in the PBE, scaling back up with levels or something. Maybe attach the healing to his passive, so that it can scale w/ levels? 12% on the PBE is IMO still too high for laning, it should start at 8% and climb up to 12 or 15% with levels. Still, even if they change that it doesn't fix his problem in teamfights. He's oppressive in lane but gets blown up before he really even gets to do anything in teamfights due to poor mobility/lack of inherent tankiness. Rather than his passive giving him a huge AD reward for max stacks (which just further increases his lane dominance but isn't really amazing in teamfights), it should be more geared towards allowing him to survive teamfights and the massive focus/kiting from ranged champions that pretty much invalidates his existence.
the rework doesn't feel like it really shored up darius' weaknesses, instead magnifying his strength of being absurd in lane without really addressing his overall weakness in teamfights. Garen is just miles ahead, even if his lane is weaker, simply because he's much more difficult to stop in teamfights.