Actually in his case it will be as good as armor proficiency chainmail. He can still take armor specialization hide and second hide feat which will make it somewhat worthwhile.
of course, at epic it is just a +1 bonus but together with second hide and all those barbarian bonuses to AC, you will stay at chainmail effectiveness for the most part of you career. (Especially considering that armor specialization for chain and scale needs 15 dexterity.)
I would however try to spread my stats around a bit and make it
16/14/14/8/10/13, getting superior will at epic. And disciple of freedom instead of hide expertise.
No beeing immobilized during your turn is a pirority for a barbarian. Especially when you consider your not too impressive will defense.
A 16/14/14/13/10/8 Spread usually makes the most out of your stat points. And when having perfect matched stats for main and secondary attribute, you can hardly do wrong.
At level 11 with 1 feat using Dex as a secondary a Barbarian will have 28 AC. That is level+17, one shy of a standard Defender. Chain is 26 (also requires a feat and gives you a speed penalty). The riders on Barbarian powers are
not powerful enough to justify that when melee strikers are so fragile, especially since the incidental benefits from Dex (initiative, good reflex, feat qualification) are even more valuable. HAE is identical to Chain (26) at level 11... with
two feats, not one. This gets progressively worse, till epic where it ends with 43 AC (two feats, HAE+Second Skin) vs 48 AC (one feat, Second Skin). Note it is possible to skip Second Skin and have standard melee striker AC of level+16 (46). If you go up to Scale
and get Scale Spec (three feats now) you'll get a whopping 45 AC at level 30, 3 behind Dex secondary. Assuming no ED stat boost, with an ED stat boost you'll be at 49 AC with one feat, vs 45 with three (or still at 43 because you picked HAE.. not benefiting from your stats is fun).
You have to go up to plate+plate spec+heavy shield to compete with Hide Armor using Dex as your secondary. If you
are going to dump dex, then you should absolutely go up to plate ASAP, but the benefits (the same AC you would have had anyway, a couple surges, worse NADs, worse Init, more limited weapon selection due to trouble meeting feat qualifications, having to dump
six feats into instead of one, oh, and you can't use a 2her because in order to hit the same AC you need to use a shield) don't outweigh the benefits (same AC as plate+plate spec+shield, decent AC with no feats at all, 3-4 less surges, better initiative, better NADs, easy feat qualification).
None of that is in any way debateable, those are the numbers. HAE is tolerable in Heroic, kind of (except for the fact that you don't need to take a feat if you just allocate your stats properly). After that is just starts to suck harder and harder.
So, again, HAE is a garbage feat and all Barbarian builds, regardless of what class feature they go for, will ideally use Dex as a secondary. Unless they want to burn 4 feats minimum to hit the expected baseline AC for a melee striker, and six plus having to use a shield to be competitive with Dex+Hide. And it isn't like you're tanking Con, it'll still be 3-4 your whole career.