TL;DR:
Running Crucible of the Bog, on Challenger difficulty, on round 103 is the best/most consistent way I found to benchmark the game graphics.
Here’s how I benchmark:
1- Load Crucible of the Bog on Challenger difficulty
2- Spend 15 tributes to start the crucible on round 101
3- Clear round 101 and 102 quickly; these do not matter
4- Move to the center of the arena as soon as 103 starts, benchmarking starts here
5- Do not move, attack, nor cast anything excepting healing. Let the mobs slowly die to retaliation/pets/procs.
6- Exit to menu as soon as 104 starts, benchmarking stops here.
Use Aspirant difficulty if you die too fast, or Gladiator difficulty if the mobs die too fast with this method.
Round 103 is caster-heavy, which is great to test. But it’s still random: sometimes a lot of mobs spawn, sometimes just a few do. To solve this, repeat the test a couple of times with the same settings. I backup a save game file with 100 tributes, and I run these steps 6 times until I run out of tributes. This takes ~6 minutes. Then I change one of the settings I want to test, copy-paste the backup save game, and try again. 6 runs are enough to balance out the randomness in spawns, and gives a good amount of data to compare over several setups.
I’ve done a significant amount of tests and benchmarks, and the Bog arena takes the cake, even when compared to Grove and Crags. Perhaps it’s the fact that there’s water in the center and reflections might play a role? In the middle of huge fights, the Bog is where I consistently get the worst performance of all the arenas (~20 FPS on max settings).
Now about the Crate of Entertainment… welp! This was quite a lot of work! Here’s what I found:
Using Crate of Entertainment to test is not practical: the setup is complicated and the results feel… arbitrary. If I make a cheated super-retaliation character, the fight is over in 20 seconds, and my FPS never go below 60-80; so not enough of a stress test. If I make a cheated non-retaliation char that can survive forever, the fight can last for 5+ minutes, after which there’s sooo many crates and projectiles on screen that the game slows down to a crawl (fewer than 10fps), and sometimes freezes; no matter the video options. I can’t really compare the performance of different graphics settings this way.