As much as I don't like
as a positive example of anything, you are indeed correct. Him building tanky would just become detrimental to his intended purpose.
The problem is that he's balanced around a really annoying (and possibly unhealthy) mechanic of not dying. That's the only thing stopping him from building tanky.
Edit: Well to be fair, classifications aren't always so solid. Riot themselves said that some champions can lean towards one or the other despite being in a certain category.
The problem is that people keep thinking that tanks are just hard to kill. Now in a lot of games this holds true, but to be a tank in League requires more than just being tough to kill. You need to find ways to have people focus you, to peel for your teammates, to hold the enemy down, to engage into the fight and survive while your team follows up.
From the blog:
-Tanks: Tanks excel in shrugging off incoming damage and focus on disrupting their enemies more than being significant damage threats themselves.
- Vanguards: We like to refer to Vanguards as “offensive tanks.” Vanguards lead the charge for their team and are specialists at getting action started. Their explosive team fight initiation seeks to catch enemies out of position while allowing allies to follow-up to devastating effect.
-Wardens: If Vanguards are “offensive tanks,” then Wardens are surely “defensive tanks.” Wardens stand steadfast, seeking to hold the line by persistently locking down any oncomers who try to pass them. Wardens keep their allies out of harm’s way and allow them to safely deal with enemies caught in the fray.
-Fighters: Fighters are durable and damage-focused melee champions that look to be in the thick of combat.
-Juggernauts: Juggernauts are melee titans who relentlessly march down the opposition and devastate those foolish enough to get within their grasp. They are the only subclass who excel at both dealing and taking significant amounts of damage, but in turn they have a tough time closing in on targets due to their low range and extremely limited mobility.
-Divers: Divers are the more mobile portion of the Fighter class. Divers excel at singling out high-priority targets to blitz toward, immediately forcing those targets (and their teammates) to deal with the diver’s presence. Divers are not as durable as the tanks or juggernauts of the world, but Divers can take their fair share of punishment while bringing enough damage to be a real kill threat if left unchecked.
Now of course there are going to be overlaps, but not enough to say that
or
are fucking tanks. Especially since they were two of the four champions used in the juggernaut rework, which made it an official subclass.