I created a set of Dragon Scale armor with 100 smithing and improved them to legendary, they had an armor rating of 584(502 without the shield). Here are the individual ratings for each piece of gear (with 5/5 light armor skill bonus[100%], 25% all light armor bonus, and 25% matched set bonus).
Armor - 232 Boots - 84 Gauntlets - 84 Helmet - 103 Shield - 83
This adds up to 586 (or 503 without the shield) and yet the armor rating I get is 502 without the shield, and 584 with the shield.
I took another set of dragon scale armor and made and improved them while wearing +100% bonus gear to smithing. I got gear with much higher ratings as follows ..
Armor - 300 Boots - 119 Gauntlets - 119 Helmet - 138 Shield - 102
And I still get the same armor ratings, 502 without shield and 584 with shield.
Has this worked properly for anyone else? Could it be a bug? Is this intended? Any information would be helpful =] I'd really like max armor resistance without the shield on.
UPDATE - I took my original set of dragonscale gear back to the workbench wearing my +100% smithing gear and was able to "upgrade" that set to legendary with the new armor ratings and that set worked just fine, must have just been a buggy set of dragonscale gear. Selling it to a vendor and rocking my 674 armor rating without a shield =D
Thanks for the help/ideas guys!