Well in 6.0 they're implementing the WoD raid sizes to SoO so 10s and 25s won't even exist at this point, so they'll probably apply a lower scaled version of instances in the new 'heroic' and 'mythic' since I'll doubt they'd make a cutting edge feat of strength for Mythic
Normal SoO needs a nerf? Really, like REALLY? No, it doesn't. Just no. Does heroic need a nerf? No, I wouldn't say so, they already made adjustments to the 3 "hardest" bosses prior to garrosh, so there is really no point nerfing them anymore.