You can always contact Gree and ask (en-support@gree.net), but presumably not being able to fuse/combine them is intentional (I've seen other people mention it as well, but perhaps because these are "new" SF's that didn't previously exist.. not sure).
They may change that in the future, of course, and perhaps it's not intentional (maybe it's a bug), but unfortunately no one here would know. Only Gree would know for sure.
-M
I think the SF fusing was listed as season SF + same season SF or season SF + eternal SF. Heroic SF likely fall in neither category.
That's a very good point. Since the changes were made to fusion, there are very specific rules (no fusion/combining of different rarities, etc.), so I would guess this falls under the same type of rules/restrictions.
I have actually had success in fusing certain heroic armors. I know guildmates of mine have had similar results. I just dont know the rules around fusing them. From what ive seen the armors have to have at least one element in common, and dont result in a seasonal sf. Thats all i know
They must have updated the fusion system again, because according to friends of mine, you can now fuse Heroic SF armors together, and apparently elements -- just like it is with other armors -- don't seem to make a difference.