NFPA 70E Art. 130.7(C)(6)(b) "Arc Flash Protection...The apparel described in 130.7(C)(13)(c) shall be required for protection of hands from burns."
"130.7(C)(13)(c)(1) Leather gloves shall be worn where required for arc flash protection.
(2) Where insulating rubber gloves are used for shock protection, leather protectors shall be worn over the rubber gloves."
FPN: Insulating rubber gloves and gloves made from layers of flame-resisting material provide hand protection against the arc flash hazard. Heavy-duty leather (e.g., greater than 12 oz./yd2) gloves provide protection suitable up to Hazard Risk Category 2. The leather protectors worn over insulating rubber gloves provide addtional arc flash protection for the hands. During high arc flash exposures, leather can shrink and cause a decrease in protection.
HRC 2 = 8 cal, so there's a start. Table 130.7(C)(10) Note 2 (which is found at all Hazard Risk Categories, up through 4) says "If rubber insulating gloves with with leather protectors are required by Table 130.7(C)(9), additional leather or arc-rated gloves are not required. The combination of rubber insulating gloves with leather protectors satisfies the arc flash requirement."