Plague is probably S/A tier now
Vs all the medkits and boon totems where survivors heal mid chase before killer can catch up, plague is actually strong as hell.
I've been using monitor, agitation, blood echo and lethal pursuer and I must say I've been getting 9-11 hooks in every game constantly. For addons I'm using green increased vile purge effectivity and green charge time for both purges. You can fully break survivors when hitting around 60-70% of your vile purge charge.
Monitor and lethal pursuer helps sneaking in on people early on. The faster you get your first infection, the better.
Agitation allows for very fast transportation to hooks, which is probably the only thing you don't wanna waste time on with this killer.
Blood Echo is kinda insane, even if survivors don't cleanse, you can deny most of their exhaustion perks, especially dead hard, at almost all times in mid/end-game. This makes plague chase potential epic even without corrupt purge as survivors can't just extend chase by another 30 seconds just by pressing a button.
With the buffs her power feels smooth and effective to use. She also fully counters the healing meta, which has been going on for very long and now is enhanced by boon totems.