Maybe I will design talent and abilities for Assassin like I did for Sub in previous post to show what Wordcannon was talking about, and to show what we lost.
In Claasic and TBC for example Assassins talent tree was literally build from crits, dmg bonus, and increased chance of poisoning the enemy + more energy on top. In time we got additional talents to regain combo points, gain more energy during some attacks etc. = more burst. Then Mutilate has lost it connection with poison making it simple white dmg ability, in Legion Sin get strong affinity with bleeds dmg taken from Sub (r.i.p. Sub) and in Shadowlands we get what we get (big nerf then some buff). When Sin lost his burst he became rather a DoT spec like Affliction warlock than burst spec. I think it was made for purpose to distinct the spec from bursty Sub.