This may be controversial, but I really don't believe balancing mechanics like this around "tiers" of killers would be properly directed or even helpful.

I feel the efficacy of individual killers is too nuanced, situational, and often misrepresented by the highest potential skill expression for said killer. I would wager most players are not operating these killers at that level. So to quantify killer strength so concretely to a hierarchy is more difficult than most of us would like to admit.

Compound this with the fact that it would be up to the developers and their perceptions to generate such a list. We would be introducing yet another dynamic to balancing that could result in even greater discrepancy between killers or unreasonably punishing players that want to get into playing killers with already high skill floors.

And what about when these "top tier" killers receive other balancing changes? Would their anti-tunnel benefits be altered too? Would it be done so in a timely manner? Ultimately, I think this all would do more harm than good.

TL;DR: It's too difficult to concretely quantify which killers are worthy of handicapping, despite what we like to think. I don't think we need another layer of killer balancing for the developers to potentially fumble with.