Here you can compare to this:
https://www.warcraftlogs.com/reports...done&source=16
We are the same ilvl too. Mine is not amazing really, I could do better with prio targets, but it's still decent enough.
Basically a good use of F&B allows you to quickly roll trash mobs into execute zone and dispatch them (Iron Dragoons are not dangerous, but they are actually a pretty significant source of tank damage taken, so you can't just ignore them for a long time either), then you can abuse the shit out of Shadowburn to refill embers or cleave and then put extra free Chaos Bolts you gained into prio targets.
You do need to be careful to not trigger multiple Felcasters though, so don't AoE packs that have 2 heavily damaged felcasters ready to pop in them.
The idea is simple here, it's true that ultimately AoEing trash is a poor choice vs killing priority targets, BUT with Destruction warlock this can be easily turned around by the fact that AoE ultimately
feeds your Single Target by giving you silly Ember generation and cleave possibilities which directly transfer into you dropping F&B and nuking the crap out of prio target. Then of course the fact that you ultimately damage secondary targets that do need to be killed is a bonus.
Also note the fun part - Shadowburn should be the most casted spell in this encounter for you, for example in my parse I had 70 casts and 89 hits (so I cleaved it 19 times) and it actually did most of it's damage to the priority targets too.
Finally just to give you another small bump: I have spent about 3 times more Burning Embers than you over 7 minutes time frame simply thanks to me generating tons of embers via AoE and Shadowburns.