How seriously does the chain of command take NCOERS in the Army National Guard/Reserves?

OERs/NCOERs are just as important for the National Guard and Reserves as they are for the Active Component. They hold the same weight. They use the same standards for evaluation. They have to, by law.

In the guard it's a very big deal, It can make you or break you when you get to the promotion board. In the guard there is only so many spots to transfer within your state, unlike active duty where you can PCS for a position anywhere. Having a good ncoer along with applying for the proper schooling to be advanced to the next rank is critical. You don't have to be hot shit on paper, but your rater and senior rater should have confidence in your potential lead and take responsibility for your troops.

They take them very seriously and are included in the commander's and (I believe) First Sergeant's evaluations.

"Dude, you know what I am trying to say? Both branches are part-time components, they don't take things seriously like the active component."

That just speaks to your ignorance. You seem to have a very limited understanding of the role that the Reserves and National Guard serve. For instance, troops from the National Guard have been a part of EVERY conflict the US has been involved in..going back to the earliest Guards unit form in 1836. Perhaps you are aware of the fairly recent reorganization of the Reserve Component from a Strategic Reserve Force to an Operational Reserve Force? Not only do the RC have to maintain a readiness posture, they do this while maintaining full time jobs. The Operational Reserve Force combined with National Guard Forces have played, and will continue to play a major role in our national defense. Believe me, when I say we take things just as seriously, if not more so, then the active component.