So the way i see it DDO has broken the AC balance that somewhat exists in the PNP D&D game. (with a good DM and house rules) Creating a situation that allows crazy AC builds in no armor and it really isn't that hard to do.
Things to possibly change IMO.
1. Greatly increase the DR possible from armor and allow it to stack with innate DR from a Barb or whatever. Example: Add the enhancement plus to the DR of ADM armors or other armors like that. So Adm FP+5 would be 8/- or a adm BP+5 is 7/-. Come up with some special armors that are super-reinforced that have like DR 10+enh/Adm or something like that but -2 dex bonus AC. Warforged would need something else here like +1 dr level/3?
2. Because it seems impossible to implement flat-footed and suprise correctly. The dodge and dex and monk AC bonuses are sometimes overpowered. How would any of that work if you don't see that arrow coming from 100 yards at your back? How many attacks can you use this against in one round? Armor is always on your back. Keeping the scale for high-end armors is just not ok. Why is FP 8AC+Enhancements? The dragon armor is already 10+enh right? Why not 14? 16? Shields too.
3. Please stop with the "special" item properties that can only be on those two or three special raid loot items. Make the really powerful ones like +3 dodge ring min level 15 if you want or whatever seems ok. (natural armor, dodge, whatever.) The raid items get the distinction of having way more stuff on one item than would normaly be ok.
4. Don't nerf anything. Just make it a balance. Wearing armor should not be only for those tunes that can't or don't take advantage of the current system. AC should always be a choice that every character makes. I.E. do i want to wear the 4 items that make my AC higher or the four that make me do much more damage?
Last: The current highest no armor AC builds will still have the highest possible AC. It shouldn't ever get past about +15 possible advantage though. In a D20 system this is not ok.
I know that in PNP there are possible issues like this too. With a good DM and house rules it just isn't allowed.
P.S. The best items in the game should never be something you can make IMO. It takes away part of the essence of D&D right there. I.E. get ubber sword after incredible battle=good(raid)