You're not necessarily doing full BRD runs at low levels. There's a bunch of quests you can do at 52 onward already and the loot from the early bosses is already nice. Same with the other high level instances, there are quest groups doing them before hitting 60.
you agro a lot of mobs that people normally skip
That's true for any instance but there are more BRD groups than just level 60 Emp runs happening, I would assume. At least there used to be when I was still in my 50s.
Sunken Temple is a good indicator, op. If you can heal ST without major issues, then BRD won't be too much of an problem. ZF is way easier than either ST or BRD so having no issues in ZF might not be proof that you won't struggle later.
For BRD, make sure to get the following quests - this is Alliance side. Google up the respective Horde quests if you need to:
1. In TANARIS, talk to Yorba Screwspigot. This nets you the goblin head in the bar.
2. In BURNING STEPPES, talk to Helendis Riverhorn. This starts Onyxia attunement chain.
3. In BURNING STEPPES, talk to Jalinda Sprig. This starts the fire elementals mini-chain.
4. In BLACK ROCK SPIRE, talk to Franclorn Forgewright when you're a ghost to get the quest for the key.
5. In BLASTED LANDS, talk to Enohar Thunderbrew. This nets you the beer quest in the bar.
6. In BURNING STEPPES, talk to Maxwort Uberglint. This is for the vault.
7. In BURNING STEPPES, talk to Oralius. This is an easy kill quest in BRD.
8. In IRONFORGE, talk to Royal Historian Archesonus. This starts the Emperor/Princess chain.
9. When you do get to the bar, remember to talk to the succubus, Mistress Nagmara. This quest cannot be "pre-completed", so just do it after your first run and turn it in in your second.
10. In BURNING STEPPES, talk to the dragonkin Cyrus Therepentous. This will get you killing the giant inside BRD.
So that's 10 quests/chains. I've probably missed one or two as well. Together they will net you hundreds of thousands of XP.