This doesn't make sense to me...from what I've read on this Legendary skills thing, it simply resets a skill to 15, permitting it to be raised to 100 again and with those potential extra 85 skill ups per skill, increases the level cap. It doesn't mention going above 100 or even "increasing the amount of damage". One would assume that the same skill re-raised to 100 will be no more powerful than non-legendary 100.To put it more simply, improving your sword fighting skills beyond that 100 point limit is now possible, but will only increase the amount of damage that particular skill is capable of generating and won't offer you new skills or any special attack animations.
Unless the Legendary status comes with a bonus of some sort. And though the level is significantly higher, there is still a cap present, though I have no idea what it could be. I believe raising every skill to 100 as standard results in partway between levels 81-82. Another 85 skill ups for all 18 "legendary" skills...I'd be interested to test this out of curiosity.
Still, it's largely pointless. On a normal playthru, one can realistically get as high as mid-40s by which point most things aren't threats. I made it to 60s on my last (sorta current) playthru with Dawnguard added in. Legendary Dragons (I think lvl 60+) are the only thing I've found that can kill me without genuine effort for my part. Most things simply stop scaling well before this point. I think the highest levelled, scaled enemy is about 50ish. The highest lvl summon I know is lvl 38 (perma storm atronach).