I've seen a tank get chaotic before when he is collecting orbs. I don't think I've seen the tank that currently has Ramuh get chosen for chaotic though. Either way though, if it happens, like others have said, that tank just needs to get back in position before it takes hold. The boss frees the tank with his attacks.

What's with this solo tank method though? Sounds like if you are learning, you'd be better off doing a duo tank method anyway, unless can't kill the adds fast enough. If that's the case though, instead of going single tank, I'd just have a caster limit break a few of them. Single tank just sounds like a pain in the butt. Remember the days with the egi tank? Summoner dies and bam, wipe. Same with single tank I'd bet.

Even during the days that the egi tank was still a viable option, I usually voiced against it. That strat was always more trouble than worth, unless you just had really low dps.