I think I was pretty angry when YS changed, as I was a gnome wearing HP/LP exclusively. Since then I've spent a stupid amount of time in baby celps backtraining weapons, lores, and armors in a dumb as rocks 4 armor set up with store bought garbage. Worked fine because I was at cap for defenses plus warmages have enough buffs to be invincible anyway.
I tightened things up in preparation for moving to super celps because, well, i was bored of baby celps. Went to a light chain set up and swapped out legs to lock the others. Made some slick changes to my buffs so they basically never drop. I transitioned to supers perfectly, not a single issue. Don't need healing for 12+ hours. So I'm like what the heck. Why don't I try a stupid 4 armor set up with what I have on hand.
Turns out the 4 armor penalty is really nbd. I wear leather legs, chain hands, brig chest, plate on the rest. The brig and plate are lumium, the rest is trash.
That said, I think it's probably a terrible choice for people who aren't getting big bonuses from SW and SuF at a minimum. Once you're capping SW/SuF/AEG, I think armor really just becomes about fashion for us. At that point you're probably also keeping MAF up to cover the "natural 20's" that hit you.
What I mean is, there's really no ceiling after which a certain armor set up becomes strictly non-viable. Prime players may want to climb the ladder faster than I do, but keep your defenses appropriate and use the most important spells in our arsenal and it's really a breeze.
I'll try to update this in a few months when I go to... wyverns i think? Special attacks may change things.
As for best armor--right now: cloth. Titaneese. No contest.