My biggest complaint with armor nowadays is that a lot of vehicles with light armor are weaker than they were to begin with, now that you can just glance them to death with volume of fire. That makes autocannons useful I suppose but transports are even worse now (imho), especially rhinos - it isn't really hard for just about any army to get 3 glances on AV11, and you can still get popped by penetrating hits. Melee lists using rhinos has been meh for a while but it seems like most people, if they do use rhinos and such, go with a focus on dakka so they don't have to worry not being able to charge when disembarking and other such issues. Dark Eldar vehicles seem to be less affected since they weren't ever intended to weather heavy volumes of fire and are much more mobile, but I dunno. As a CSM player who likes to run melee lists (and I have since at least 2nd ed iirc, and I don't think RT would count) rhinos have been shit for melee transport since like 4th ed iirc when they decided to nerf rhino-rushing, I can't deep strike but a handful of units, no drop pods still, Chosen no longer get infiltrate, Land Raiders are too expensive to be able to transport an entire CC assault list and in order to be able to infiltrate as a Warlord Trait I either have to take a 1 in 6 chance and hope I roll "Master of Deception" with a vanilla Lord (and even then it's only D3 units) or I have to take a special character that already has MoD. And since that's either Huron or Ahriman, I'm not going to take Ahriman with a CC list so I guess I have to take Huron then! (and hope I roll a 5 or a 6). I thought about the Forge World transport flyer, but it's about the price of a Land Raider anyways.
I fucking despise taking anything that is AV12 anymore too. Dreads? Yeah, GL with that. All of the AV12 stuff in the CSM codex (maulerfiend, forgefiend, dreads and defiler) just get picked apart and glanced into the dirt. And what's crazy is that they gave the Defiler and both fiends "daemon" for a 5++ and they also have "It will not die", so they must have known that AV12 was a fucking joke or they wouldn't have felt the need to give that stuff to them in the first place. As anyone who has ever played any flavor of Daemons can tell you, 5++ is only useful for the occasional lascannon potshot; any serious volume of fire is just going to make a mockery of a 5++ save and "It will not die" only works if you end the turn with wounds or hull points remaining so people just focus fire and pop them so you don't regen shit. Last game I played (which was a while ago now) I had a fucking Chimera glance a 'Fiend to death. A fucking Chimera.
Also fuck flyers, fuck them right in the ass.