I'll start by saying I like most of what I see, but I feel a few tweaks are needed.
My initial concern after reading it was, why wouldn't a barbarian's first feat be chain armor? Since they don't rely on Dex or Int, it seems odd. Most barbarians will feel obliged to get this feat, and even possibly follow it up with light shield and scale. That's such a boring path of feats. Since 4e is trying to get away from the auto-pick feats, I think this issue needs to be addressed.
I also don't like Rage Strike at all. It's a waste of space. There is no way I want to encourage a character to give up a daily power to nova in one encounter.
I would gut out Rage Strike (don't see any need for it), and replace it with a class feature that allows the barbarian to use their constitution or charisma as an AC bonus instead of dexterity or intelligence, if they are wearing light armor. This puts them on par with two weapon rangers and warlocks.
If the intent was to make it so Barbarians are easier to hit, but can absorb more damage (as the class description seems to indicate), then the class is not going to work as is. Chain armor is way too tempting to resist, though I guess this isn't terribly different than the wizard and leather armor.
I don't have a problem with the way Howling Strike works aside from paragon multiclassing concerns. That part can easily be fixed by imposing some sort of requirement without changing the mechanics.
This class also suffers from "everyone can do it but dragonborn can do it better" syndrome.
Rage strike isnt made to encourage novaing it is used to enable novaing, like every other class can fully benefit from burning multipule dailies in an encounter. The barbarian without would override his first daily with his second. This is a problem if the first rage buff is more effective then the second but the barb still feels the need to unleash daily calibar damage.
no comment on the armor issue but on the dragonborn issue.
STATEMENT: R.I.T.M.(Rage in the machine) SURPERIOR, SCALY FLESHBAG INFERIOR.
Seriously, warforged frenzy barbs don't go down until negative bloodied. Granted when they go down they stay down forever. Also same stat bonuses and the warforged racial that heals when bloodied and gain temp HP is totally up the barbs alley