Have a look on the armor enhancing calculator by Barbanium in the Fan developed resources thread, with it you can compare different alternatives. And based on that, I realized that even if I get only 20ep from Snakeskins, they are still the most efficient way of enhancing Ravenlords Mantle up to the fusion stone stage around lvl 55.
http://www.funzio.com/forum/showthre...oped-Resources
SCU's are excellent when you are away from game like a day for offline reasons. Also consider Swamp Shaman Robes in some cases, but Roc Feather Robes or the later armors are not worth their cost/time compared to fusion stones.