It depends, from what I've seen. I don't understand the exact formulas they use, but percentage increases, like a skill that increases stamina regen by 30%, will increase out-of-combat and in-combat recovery by that percent. Flat increases, like a necklace that adds 55 stamina recovery, don't seem to affect out-of-combat recovery, though they do affect in-combat. I've been using the Harven's Extended Stats addon, which may not be updated for 1.6, so that's the basis for my conclusions.