It is ridiculous that only full plate wearers (edit: and superpowered AC multiclass builds) who meticulously plan and dedicate everything to AC can get to the point where a high-level monster will miss them on rolling a 2.
In PnP (and even Neverwinter Nights 2), cloth and light armor wearers can invest even moderate effort into raising their AC and it will matter, even at level 20. Not so in DDO.
If you have more than the minimum Dexterity for your race and you don't use it for skills or Finesse, I hope you do better after reincarnation, because you did it wrong.
I don't want to undercut my point by exaggerating. I know that some light armor wearers, with the right multiclass choices and extremely high quality gear, can get AC high enough to make some amount of difference. But it's out of reach for most players.
Something so basic as armor, out of reach. Can you imagine?
The solution is to nerf monster attack to a point where a cloth or light armor wearer can invest in AC and not be hit automatically. Unfortunately this would mean tanks as they are would be invulnerable, so tank gear must be nerfed.
Please, try not to get hung up on the particulars of my post with nitpicking. I'm sure there are a handful of anecdotal exceptions. The driving point of my post is accurate. It is way, way too hard to get AC to a point where it reduces even one point of damage taken on a quest.
Edit: The issue is not that only high AC builds can get high AC. It's that no one else can get enough to even matter. The best they can do is some lower number that may as well be 0. AC should matter for everybody.