Here's the thing about Assassins being ran as tanks
Eventually as you play characters like
,
, or pre nerf
, you'll notice that you may not help very much late game because everyone on the enemy team is tanky and your burst just isn't enough to kill them. Now you know your only option is to somehow make yourself stay in the fight longer. And you do this by building tanky. The above champions just happen to have kits that allow this to happen. People build tank Ekko and tank Akali to be better team players. Even as you're fed as assassin Ekko or Akali, late game everyone just groups and you'll be lucky to get even one kill. These are not intended things these champions designs.
Although her and annie are conditional. It's not hard to do.
That's everyone with some form of point and click hard CC from ranged to melee range.