Naut Change is not enough. Riot you barely touched the problem
So everybody knows about the change to health on his w. This is great minus the fact they should of done this last season. With Riot constantly lowering the total health of the game this change was required to even make Naut usable. Sadly this does not address the problems that this champ has.
The problem is that Naut mid game late game means nothing you are totally at the whim of your team mates. The defensive stats you must get to try to soak damage make you a joke. Try to 1v1 any non tank that is equal gold in items and watch yourself get melted. Also God forbid that you are caught in your own jungle by any enemy champ.
Naut needs some king of threat mid late game besides his CC. The CC is pretty much meaningless since almost all of it used to start the fight (R & Q). Teams can decided to either quickly focus fire or ignore any naut if his ult is already down. With some much pen in the game the shield breaks breaks to easily and reduces any threat he may actually have. Most mages can delete the health shield with one spell.
Tanks need a threat to be focused. Threat does not mean only damage though riot has only ever given damage threats real meaning. Constant CC can be a threat but naut does not have this, nor does his kit even come close to supporting this. His damage values are a joke even with his shield up. Riot expects jungle tanks to build AP but give no reasonable path to do so while being a real tank.
TLDR The issues are deeper than just a shield problem. All riot has done is put in a change that is 2 seasons to late. More is needed.

... during ultra rapid fire mode were he was an unstoppable force early game. That being said I will need to agree tank champions have it hard trying to build up both health and attack.