Thanks for the tip Tails. If I understand you correctly, the debug value shown is for the head level light, not the light level of the block I'm standing on?
I don't use any mods, so I assume my jar is un-modded. Not sure how I can prove the light level is >7 everywhere, but I walked the entire level where mobs are spawning looking for any torches endermen might have moved and verifying that I had at least a BL of 8 everywhere. Any chance a copy of the world might fix my issue?
Screenshot of mob
You guys are great. I'll move stuff around and see how it goes. Thanks for taking the time to educate me.