Barbarians are by nature followers of The Tribunal, as such I don't believe they can follow Rallos Zek in the first place. So the construction of Barbarian armour for a Rallos Zek follower would seem to be a little pointless anyway.
The only warriors that can't worship Rallos Zek are Dwarves and Iksar. Barbarian warriors can and do worship him, so there would be a reason for there to be a Rallos Zek deity armor wearable by them :P
My appologies, perhaps I should have made myself clearer. While barbarian warriors may well be able to follow Rallos Zek the armour itself can only be made with the help of a Shaman who follows Zek as it requires the use of Imbued Jade. Barbarian shaman follow The Tribunal and as such get Imbue Ivory as their deity's gem of choice... it would therefore only be possible for this armour to be made by a collaboration of effort for Barbarians to be able to wear it.
Besides which... Barb's get their own armours anyway ;-)