Is this a common thing for tanks to do?

[fm_fenrir]

Turning around for a second to overpower, stopping until vuln fell off, just saving flashes to make sure every mob is hit, all better options than running off with huge damage incoming without being able to accept any heals safely.

You can't stop on a big pull, because the instant you stop your DPS think you're done and start laying into the mobs you already have. It almost invariably turns into a wipe when you continue the pull and your DPS are still beating up things you only hit with a single overpower.