In one of the screencaps for ROCH '06 that I saw in Ghaleon's photo album of wuxia images, I noticed that this depiction of Gwok Jing wore Sung-era military battle armor during his defense of Seung Yeung Fortress in the series.
Did Gwok Jing, in fact, wear battle armor during his skirmishes against the Mongol forces in ROCH? I figure that Gwok Jing did wear battle armor in LOCH when he led the Mongol armies against the Jin and Khwarezmian forces, but that was because he was an actual military commander with an official position and title in the Mongol army during LOCH. In ROCH, however, he was a civilian volunteer, and moreover, his wulin fighting style might be constrained by inarticulate, heavy battle armor. Hong Lung 18 Palms and Left/Right Hand Technique weren't really designed with an armored user in mind.