Things that don't belong on assassins.

How does sustain (by which I assume you mean lane sustain) fall outside of the assassin identity? Genuinely curious why you think this.

Poke I can see if the assassin can already all-in without it. Assassins like Talon need to poke because they literally cannot 100-0 early. Assassins like LB do not (and she doesn't have any poke worth discussing).

Are you trying to talk about

Sustain is fine, an assassin can be balanced having sustain, as long as it's there because he/she needs it for laning or it's mechanic they absolutely need to survive in fights.

AOE CC shouldn't exist in an assassin's kit.

They should have poke in most cases, but not strong poke UNLESS that poke is harder than average to hit or they can't all-in someone. They can or cannot have sustain, that doesn't matter. I don't know an Assassin with Bruiser or Tank stats unless built to do so OR they are an Assassin who has no escape (rare). Point and click crowd control is pretty rare on Assassins and is usually needed in their kit when it is. Shields fall under the same thing as my explanation on Bruiser or Tank stats.

Assassins should be defined by quick thinking and high risk-high reward. The problem with the latter is that the boards usually dismiss that component as either terribly underpowered or horribly oppressive and overtuned.