Seems a bit unnecessary given Naut's W is about 90% of his clearing power and you already compensated for the E cooldown reduction.
Naut shield does not really scale well by rank, it will be weak early game and strong late game no matter if you max it or not. Why do you max it? To get damage to clear.
The point on this changes is that he max first E to get better clear, so he doesn't have to waste early ranks on a shield that doesn't really scale in order to clear properly (and, while he has sustain to jungle, he's extremely slow clearing it, so it's fine for me if they buff his clearing speed).
Whether I'm underestimating the extra power of the E reduced cooldown
You are: consider he's getting a CD reduction from 10 to 4 (which is pretty huge). Mathematically speaking, he will be dealing 150/250/350/450/550 +0.75 AP^ every 10 seconds (right now he deals 60/100/140/180/220 +0.5 AP every 10 seconds). So imagine clearing with 350 damage on his E every 10 seconds at level 5. Seems like a huge buff to his clearing speed.
^Cooldown at earlier ranks it's 6/5.5/5/4.5/4, so he'll be dealing a bit less damage than I said early game, but it's still more than the current damage.
Btw, Meddler mentioned "Yeah, to be clear - we want this to be a buff to nautilus. We're watching the W changes heavily." so if these changes end up being a nerf (and I really think it will be a huge buff), they'll undo it or modify it to be a buff. This time RIOT did it well.