Well, are you still supposed to max W first?
Assuming 600 health, ranking W only increases the shield strength by 20 compared to the previous rank. Nautilus most likely has 600-700 max HP at level 3.
At 1000 health, ranking W once then gives 30 health. It is still less than the previous flat 50 per rank skill growth.
Only from mid to late game does the shield become better.
I thought Nautilus had trouble clearing early? Isn't this a nerf to his early clear? I may not have considered the recent jungle changes when arriving at my inquiry.
Edit: Oh well, I suppose his 1-3 actually got better from the actual shield values, not the shield strength increase per rank. My bad.