Naut doesn't need more cc or dmg on his ult because his post 6 strength is not the problem.
I don't mind the passive buff, but I'd prefer a damage buff on it, to give him a bit more burst as I doubt this cc duration increase will change much. Cos if you've been cc locked by naut you're probs dead anyway if he's got help (which is usually the case when ganking)
His problem is his low mobility compared to many other champions (EVERYONE IS FASTER THAN ME WHEN I GOT MS QUINTS ON+swifties), crappy clears (as a result of damage nerfs), his reliance on core items (he's a lil feast or famine) and the slight mobility boot cost increase.
These both slow down nauts early game ganking potential like crazy and place him under enormous pressure to get sh*t done, as power farming is not an option for him (braum jungle can power farm faster than him... without splash dmg) . It's slower as he has to farm more camps with slower clears to achieve his first power spike with mobility boots. And since top lane is no longer a prime target (naut sucks at herald) you're limited to the 2 shortest and hardest to gank lanes for a nautilus (to maintain drag control)
I'd personally like his W dmg to scale with his hp, like its shield strength as opposed to ap in order to boost his clears after cinderhulk.
Another potential fix for when he has no choice but to power farm (lanes are to fed), would be to change immolate (cinderhulk passive) to sapping barbs ( the old spirit of the ancient golem passive). This would allow both it and a sunfire to be bought for clear speed. Which wouldn't be an attractive option for champs like sej, grag, rek sai or zac as they can already clear the jg faster than it can respawn while weaving in ganks. Resulting in a wasted item slot as sapping barbs didn't affect champions ( Could've been a dead mans, locket or randuins instead).
Just my 2 cents.
[slayer-jinx-wink]