Immortal Spelunker

Title isn't accountwide unlike it's listed on wowhead

YOU DO NOT NEED TO SOLO THIS. If you do decide to solo it, remember that it's not balanced for each class so some variants will be impossible for your class/spec.

Recommended story variants:
[zone=15009] on Runaway Evolution (there is no final boss)
[zone=14998] on The Great Scavenger Hunt (non-combat objectives)
[zone=15003] on Lost Gems (many skippable packs)
[zone=14957] on Explorer's Competition (non-combat objectives)
[zone=15002] on Captured Engineers (the boss [npc=214263] does mostly avoidable damage, heal/pop CD through Burn Away)

NOT recommended story variants:
[zone=15009] on Torture Victims (last boss [npc=219856] is very difficult)
[zone=15007] on Tortured Hostages/Strange Disturbances (last boss [npc=220510] is difficult)
[zone=14999] on Kidnapped Earthen unless you have Spell Reflect/Decurse for final boss, or a very short cooldown interrupt.

You can check the variant at the door before you enter.

Recommended Brann set up:
[spell=459061]
[spell=458955]
DPS spec for execute.
Switch him to heal for the final boss.

If Zekvir randomly spawns, run for your life until he despawns.
If Tala & Velo miniboss spawns, avoid them or CC and deal with them one at a time.
If you're ever in trouble in general, just kite and let Brann whittle down the enemy.

Use all your CCs and abilities at your disposal. E.g. Monks can use [spell=116844] to skip or break up large enemy packs. Priest can use [spell=605]. Stealth makes some objectives trivial.

Is this no longer achievable? I can't get it despite not dying...