Yep, armor only provided 3.33% protection per point, and there are very basic armor penetration mechanics that I think might have been removed (they basically amounted to "deal more damage to ignore armor", i.e. deal more damage in one hit to boost that damage even higher, hence why creepers managed to be fairly devastating with point blank hits in the snapshots).
Sadly, nerfing armor only serves to make the creeper even more binary.
Overall, however, I do like the nerf. Mobs in general are are a much more fearsome element in the game, making one have to think twice about their worldly excursions, be mindful of their surroundings. I do think their durability could be improved a bit. Diamond seems to get eaten up very quickly.
As for creepers: they do have some really annoying mechanics but overall I think they're not that bad of an addition and only really need a few fixes to make them better.
They're good in that they require a vastly different skillset to counter in comparison to most other mobs; while the others will kindly alert you to your presence so you can beat them with a sword and won't be too devastating if you let them sneak up on you, creepers require you to maintain a constant awareness so they can't oneshot you (but are the weakest mob common mob if you know that the WASD keys exist if you catch them). They're also a good bit more unique than zombies, skeletons, etc. even if they are the byproduct of a badly-modeled pig.
Actually, I'd say zombies are the weakest common mob. They don't do nearly the same amount of damage as a creeper and also require you to be within arms length. As for unique, it depends on what you mean by "unique". Skeletons fight in a much different way than any of the other mobs. Creepers' basic mechanics of approaching a player and inflicting damage, which is literally the only mechanics they possess, are pretty common.
The problem I have with them is that they're typically going to kill you in areas around your house, where killing the player doesn't hinder them notably. They'll just walk back, grab their stuff, and be left with a disorganized inventory and a hole in the ground (plus lost EXP which only matters in the endgame). They don't even have the courtesy to drop enough dirt to fill the hole back up. While a sneak attack in a place far away from the safety of a player's house is threatening, this happens less often as players will typically be expecting danger (and therefore creepers), they'll typically just end up annoying the crap out of people next to their house.
Another example of the dreadfully banal maintenance responsibilities creepers compound for players. Not only is a player's gametime eaten up by having to deal with cleaning up after creeper damage, but that time can be multiplied profoundly if they are short the necessary materials to rebuild. Travel time, crafting time, etc., all for simple maintenance. Like I've said before, there's a reason video games don't make you mow the lawn. Maintenance simply does not belong in a video game.
Fixing this should be fairly simple; if a creeper's damage to a player would exceed 19, they'll only deal 19 damage (thus sparing fully-healed players) but will inflict a variety of nasty potion effects like slowness, weakness, mining fatigue, and on Normal and Hard a new effect that greatly reduces the speed of health regeneration. In a place where a player really has no business dying, they'll just stumble back to their house (or not bother) and be good to go, but otherwise the player will have a chance to survive but will have to basically outlast the negative effects, rewarding a player for skillful play if they happened to be able to survive playing like that but simply dropped their awareness at the wrong moment. Additionally their explosions shouldn't have a chance to outright destroy dirt blocks; instead, they will be broken as expected but will always drop a dirt block to refill the hole without worry
I can't help but feel that this would only make what is a fundamentally flawed mob only slightly less annoying. Because creepers are designed to be undetectable, and to inflict all their damage in an instant and disappear, they are a fundamentally binary component to the game. If a player doesn't notice a creeper approaching (which, let's be honest, is how players are typically killed by them), they explode without any kind of player interaction can really occuring. Which is to say that the typical creeper experience occurs without any meaningful interaction from the player, leaving a player with nothing more than busywork.
To put my point of view simply, it's hard for me to imagine what it is, beyond sentimentality, that people like about the role of creepers in Minecraft over any other mob. Other mobs kill you, punish you for not paying attention. Other mobs can spring out at you and scare you. The only truly distinguishing dynamic creepers contribute to the game is that they damage your world. And I think most people are too blinded by mascot fandom to realize that having to spend time cleaning up a mess is really not something that can rightly be called "gameplay", let alone all that interesting of a contribution to begin with.