Basically most systems in DDO are much, much simpler than you think.   This is most likely to keep things flowing on the back end.

When you enter a dungeon, it takes a snapshot of your character and then places you somewhere along a pre-designed curve that is based on the level of the dungeon and the difficulty.

A good example is spell DC's.   If you enter ELite, for example, it basically compares to a checklist of all the things they've determined that a character should have if they think they can do Elite.  (Spell Focus, School DC Item bonus, what your casting stat is vs what it could be if you had everything possible for that level, etc.

It is then further broken down into 3 mob types i.e. reflex, will and fort (quick, tough, caster etc)

Basically rather than each time you go to cast a spell against a certain enemy and it rolling a saving throw, it rather most likely gives you a caster rating, factors in whether you are casting an "approrpirate spell" against that enemy type and then most likely comes up with a much much simpler formula to see if your spell lands... so rather than it being based on a D20 die roll plus a monsters save bonus taken against your actual DC, its most likely more like a 4 or 6 tier system that is based on your calculated 'caster rating' taken against whether you casted an appropriate spell against that type of monster.

So when you enter a dungeon, once your caster rating has been determined you basically fall into 1 of maybe 4 or 5 catagories for landing your spells.. either you do not qualify because you are completely out of range in which case you will never land anything, you fall into rating 1 where you land say 25% of the time, 2 for 50% of the time, 3 for 75% of the time or 4 where you always land that spell (against that mob type).    Casting the wrong spell against a mob type (i.e. casting  reflex based spell against an "agile" class enemy probably bumps you 1 or 2 ratings down.

I am guessing that AC most likely works very similarly.   There is most likely a viable AC range for each dungeon/difficulty... like viable AC range 100-116.   If your AC is below 100 you will get hit 100% of the time (assuming 0 dodge/blur etc), if its over 116 you will most likely avoid all hits (it might cap out at 90%)

As per the argument in this thread, what I am saying is that they are most likely coming up with a different formula and weighing AC differently in Hard and Elite.   In Hard they are basicalllly willing to accommodate 95% of the DDO population, which is what you mostly see in these forums, i.e people who think they know what they're doing and have a handle on things (i.e. "displacement is your friend, don't bother with AC").   But on Epic Elite (or LE etc) they are most likely looking at whether you dumped AC or not and if you did, making your defense chance over all suffer.

Moral to the story is what they are telling you is going on is not whats going on.   

[snip]

Here's simple proof that your wrong.   Stuff will not land if you fall under the range.   If everything was being done as according to a D20 system as you believe and as they are telling you, there would be a much higher variation in the results.   Playing 10 years, I can tell you... I'm right your wrong.   Reverse engineer the log all you want.. if anyone would have actually done that they would have actually found instances where enemies would have made low rolls on their saving throws and you actually landed stuff (as in yes you will land a spell when they roll a 1, 2, or 3.    But in all the 10 years Ive played and the 100's of thousands of spells I've casted, I can tell you that has never happened.  Your either in range or your  out of range. 
A) Everything is done with "ranges"
B) You are rated as according to those ranges and within those ranges.. there are a maximum of most likely 4-5 ratings, either your out of range (you fall below) in which case you will NEVER land anything, you are rated within the range, or you are rated beyond the range.

If you were right and I was wrong, you could fall below the range and still land a spell now and then, which I can tell you after  10 years and 100's of thousands of spells, doesn't happen.

I think we are all just relieved we dont have to hear this shit in voice chat.

... Most of you have a tiny fraction of my experience... the vast majority of what you think is your "knowledge" of the game comes from starting the game when TR came out at which time I had already capped and deleted around 60 characters.... 

What kind of AC do I need for LE and what % of the time would I get hit from it?

Interesting.  I really like elves and my dex ranger is an elf, but to go elf you are giving up 1 feat from human and then spending a feat to get the dragonmark(so negative 2 feats total) and at least 12 AP.  On an AP starved build.  It also costs you human damage boost.  But it does get you 2-3 more dex than you can get with human.

But to be fair, I have put some AP in the Elf cores to get some extra dex on a dex ranger, so it's not 12 AP off a normal build.  It doesn't totally gimp your build.  But there is a cost.

It is more convenient than using actual shroud item clickies and such to get displacement.   

Scimitars are a better crit profile than khopeshes...

Ah, another gullible imbecile blathering away like you understand the game.  You may want to make a new completionist toon as you apparently missed everything the first time around.  Or maybe swallowing all those loads from your guild leader who also thought he knew what he was doing somehow clouded your judgtement.

First of all let me put your in your place.  I capped around 60 characters before you started your little TR queer quest to go around and around to try to get people to recognize you with your single character.

I am the one who taught the stuff to the people who taught you.   I know better than you, by a long long ways.  Period.

Let me explain again how it works since the first time you apparently didn't get it.

All the numbers you see on your character sheet?  Meaningless.   Oh there is some meaning to it but nothing close to what you think it is.

I'll say it again for the borderline retarded like this guy (bigjunk), the system takes a rough composite of your character and then breaks it down into some much much simpler than you think.

I have played the game since 2006, believe me, I know much much much more than you do.   Almost everything that you were taught (since you never came up with anything on your own, I was the one who innovated years before the people who taught you found out about it.

Anyway as I was saying, the system asks a few simple questions before creating a simple hit/defense matrix for your character.   Did you try to maintain an AC that is adequate for the level and difficult that your doing? Or did you go the way of the stupid dumb  DDO Vault fuck and dump AC and say something gay and retarded to the effect of "blur" displacement" ghostly is your friend" As if you had some semblance of what was going on in the game.   This is why your defense tanks.  Becuase your a stupid fuck who can't stop mouthing off like you know what your doing.

This is the reason why you can get away with EH with dumping AC and going w/ blur/displacement/ghostly/dodge etc.   Becuase EH and EE create your hit/defense matrix differently.    On EE if you dumped AC it will tank your chance to defend. 

Believe me, concerning trash mobs there are only 4 classes that you fall into as to whether you are getting hit or not.    It is probably more complex with ongoing fights with raid bosses, but with trash I can tell you it is a much much simpler system than you think it is and it is nothing like what you think you know.  So accept that your  a fucking idiot and move on.
EDIT:  Oh and Bigjunk, I'm sorry if you took offense to anything I said, it wasn't meant to be offensive.

~snip~

It is easier to do all math on a completed character and let everyone subtract their own specific situation from there. 

or do all the math on a character without 36 epic lives, 42 heroic, 12 iconic and let everyone add their own specific situation from there.