Should I have taken the high road?

We ran Deadmines today with 3 warriors -- I was the tank and we had two warriors assigned to DPS.

The warrior tanking shield dropped off Miner Johnson, one dps warrior rolled greed, and the other rolled need against me and won the roll. Since he was a DPS rolling on tank gear, I asked him to tank instead of me because he had assumed the role by rolling need on role-specific gear. He says alright and we continue.

We get to the Goblin Woodcarver boss and he says he's not that familiar with the dungeon, goes in to pull one remaining mob but misses a hidden one and the boss patrols back in time to also aggro. We call him back but its too late, we've pulled. He is down to 20% before he gets a heal, the rest of us hesitate to engage because this looks a wipe. After a few seconds, the tank dies, and we run.

The healer was next highest on threat so two dps hearth out safely even while mobs run past them. Healer pops a swiftness pot to run past me, I pop a swiftness pot to run past him, he drops earthbind totem and we make it out. The only person who died was the tank and he died wearing his new shield.

Should I have taken the higher road and kept tanking since I know the dungeon better? A party member said its fair that I asked the warrior who rolled need on tanking loot to tank the dungeon, but is this partially my fault for not specifying ahead that we're doing ms > os? Should I have cared more about him staying alive?

I guess this is why I don't end up making friends in hardcore.