Revert Sunfire Buff and Deadmans nerf - Make these changes instead
Seriously Riot,
You take 100hp off of Deadmans because it's really popular. You put 5 armor on sunfire because it isn't.
Now they have the same stats, with different passives and different costs.
At all points in time, the item bought will always be whichever passive is more useful. Need to push lane? Sunfire. Need to move faster to engage? Deadmans.
This isn't item diversity, it's monotonic. With the exception of a few champions that will always prefer one or the other, everyone will go for the one that better fits the meta (which is engaging right now).
Come on, give us some DIVERSITY.
Revert the Deadman's Plate nerf. Instead make it cost 150g more. There's your nerf. Leave it as a slot efficient tank item with a cool passive, but not quite as overpowered as it is now.
Revert that sunfire cape buff. Instead make it cost 100-150g less. There's your buff. Make it an easier to rush item for earlier laning power and pushing potential.
Voila, you have DIVERSITY. A choice between two items, one that will serve you better early but will feel like it was a really bad choice if you let the game get to the point where people start getting 5-6 items, and one that makes you wait a bit longer to get, but once you're there it will feel great as part of a 6-item build.
I don't want the only difference between the armor+hp items to be their passives. You can have other tradeoffs. I don't want to see Randuin's getting changed to 50 armor and 500 health as well, it's cool as a 'slightly more armor and less health' combination in case you feel like you want that instead (although its identity is really anti-crit).
I just think you'll see players more actively choosing between Deadmans and Sunfire as an individual game progresses with these changes rather than the ones you've implemented. The current changes let you choose which is better off of the start. These actually let you react. Behind early? Better get sunfire instead. Looking like it's going to be a long game? Better invest in Deadmans.