Hello

Generally, there are many champs that are focused on either HP, def, or Atk stats. This is indicated by their skills,

Their skills will indicate(if they do damage) which stats they are based off this, which is where then you look at their base stats(via the index as this gives you a level 60 version to go off), you will notice whatever they are based on its generally higher. 

An example, we will use Sir Nic, he is an HP based champion, all of his skills indicate they scale off the HP stat, so any points into attack would not be helpful in increasing his damage output.

Be careful though there are some skills that are based on one stat and do damage but involve another stat for its effect or skills that do damage on a champion been attack based however one of their skills is based on HP

Apoth comes to mind here where his damage is based on attack stat but his 2nd skill is based on HP, However, Apoth is a utility champion and I would suggest pushing for survivability, so pushing HP would allow him to survive longer in order to support the team for longer.

I hope that helps 

Many thanks and good luck

yeah ive run into some champs that say HP based, but their skills go off other stats except that lol. ATK seems to be the only stat that can be effectively rendered useless for certain defensive, support, and HP based champions. Every other stat still has a use, even if not a skill stat. Which seems to make weapons and rings not a huge priority for those champions since all weapons come with ATK primary, and all rings will either have ATK or ATK % as a substat..