Just eyeballing it, that looks off. The lighter brown stuff is not quite as puffy as I normally see after a good first crack. It could be baked. If there's under-roasting, you'll get a lot of grass or hay flavors. The darker stuff is waaaaay into second crack, judging by all the craters and oil. I'd call it "burnt" rather than "dark." So you have coffee at opposite extremes of roasting. That's never really going to blend well. I'm also seeing inconsistent sizes, broken pieces, etc. This is not high-grade coffee.

Try asking for just the regular Sumatra at Full City and drink a little less to manage the caffeine. The flavors will be much better. What you have is so dark the nuance is gone. Not really worth the extra bucks at that point. If the roaster doesn't know what that means, definitely get a new roaster.

You should ask about the decaf process, also. Sometimes solvents are used and they don't get removed. That would explain the nastiness. Or they used the water method and the green went rancid. Either way, kind of yuck, and probably not great for your health.