Is Overkill crest or Umbra crest worth getting?

[flamealchemist73]

When I see crest recommendations for Raven why do I never see these skill crests?

[Panpeito]

as a raven, the goal is to deal as much damage as possible and as quickly as possible. overkill, even if it could be plated for damage increase or cooldown(not sure what it has) isnt a top priority for ravens because it has a long cast and pretty underwhelming damage compared to your other skills. it also does have a cool additional effect of making you invincible for 2 seconds, but the long cooldown and subpar damage makes it unworthy of cresting. umbra is a damage over time sort of deal and is also restricted to where you cast it. its nice if you get all of the damage out of it when the boss stands in it for the whole time, but sometimes the boss doesnt stand in it the whole time and there are other skills that do more damage and arent so restricted. umbra is basically a bonus, and doesnt need to get crested

[Lemon]

They're not as consistent as rake, rain of death, chain punisher, applause, and deadfall