@Zane- I'm late but can provide some additional insight.
I think the suggestion in the error message is a good one (I'm biased because I wrote it, but some thought went into it). "Memory is likely oversubscribed. Reducing query concurrency or configuring admission control may help avoid this error". The general solution for this is to set up admission control with some memory limits so that memory doesn't get oversubscribed, and so that one query can't gobble up more memory than you like. I did a talk at strata that gave pointers on a lot of this things - https://conferences.oreilly.com/strata/strata-ca-2019/public/schedule/detail/73000
In this case you can actually see that query 2f4b5cff11212907:886aa1400000000 is using Total=78.60 GB memory, so that's likely your problem.
Impala's resource management is totally permissive out of the box and will happily let queries use up all the resources in the system like this.
I didn't see what version you're running, but there were a lot of improvements in this area (config options, OOM-avoidance, diagnostics) in CDH6.1+
There's various other angles you can take to improve this - if the queries using lots of memory are suboptimal, tuning them (maybe just computing stats) makes a big difference. You can also