User blog comment:Witchking99/Saburra, The Sand Demon/@comment-25167494-20160429234817/@comment-7709681-20160503143450

No, an assassin that turns out that can be build as a tank and yet remain as assassin, or a tank that can be build as an assassin and still remain a tank, without meaningful weaknesses, should not exist. Look at Akali and Ekko for example.

As for creating Assassin/Tanks, Riot argued that, although possible (And they even indicated how), is a design so hard to become cohesive that they just don't want to try for now.