For those who actually think whats happening to Nautilus is a buff:
Take it from one who actually plays him, ITS NOT!
Nautilus starts with a Mana pool of only 284. One E costs 60 at level one. Even when you position yourself perfect, you will only hit monsters max. 2 times. Thats 90 damage. If you use it with the new Cooldown, you will end up oom after using it 5 times, or different to say: Dealing 450 Damage.
This change DOES NOT AT ALL help his early clear, and for sure cripples his lategame clear. Nautilus, despite being classified as a tank, is facking squishy without his shield. which meany you HAVE TO level your shield. And that means, your clear gets even weaker as the game goes on.
I dont know who made these changes and thought it was a buff, but I know one thing: This person never even played ONE GAME with Nautilus!
which you should have no matter what the mana cost is negligible at best. This is a straight up buff to his mid/late game and a minor buff to his ganks and a slight nerf to his W overall damage which IMO is perfectly fine with the trade off they are making.