In nautilus case i will have to disagree for the most part. I do "AD/AS Naut" but i still build rather decently tanky. Its more like a CC bruiser build. My damage isnt like Vi, but my CC is already very strong and easily applied, and by getting bloodrazor/trinity/nashors tooth (nashors tooth is only sometimes) i make my damage much more relevant to any squishy champion i get to. I have won 1v1s with other fighters like Fiora due to having relevant damage, CC, and tankiness.
And it also allows me to clear objectives much faster by myself if needed than before.
My goal is to still fulfill the role of tank, but i also want to make sure we win by keeping myself more relevant when it comes to taking things like towers (so instead of just tanking it, i smashing it down in a good time), or having the ability to solo drag more efficiently, or increasing the speed of taking a baron.
By building/playing this way, i help finish the game during the midgame or as close to it as possible before i get any more outscaled by ADCs because the game is prolonged.
in regards to AD ekko, they already did some nerfs towards tank ekko. if they saw any more problems we probably would of seen some quick changes in the 6.18 patch a few days ago. and it wasnt particularly impressive during the NA LCS Finals.
If it does seem to be a huge issue, i agree. adjust something. but i believe he's finally just getting played as a fighter and people arent adjusting to it well.