We do run with 1 tank and 5 dps, 3 of these being melee. I don't think we have had a problem with the tank getting sucked in a mind trap in phase 3 yet. Our problem comes with too many dps getting trapped in mind traps. On occasion we've has as many as 4 people in one mind trap.
It sounds like it's really a problem with your DPS then. When the boss isnt down, there's literally nothing else for them to do besides break people out of mindtraps. They only have like 20-30k health, it should take at most 6-8 seconds to break one out, even if one is mindtrapped.