How about we have the main spec as the spec you come in the raid as.   I say this because on the start of the raid, I look for number of people.   so  If one comes in as tanking gear, then their main spec is tank.   if they come in as dps, then their main is dps.  when they come in as healer, their mainspec will be healer.  I know dual spec will give us flexibility to form groups and adjust to the group make up for each boss, but main spec (imo) should be the spec that you currently are as soon as you step into ulduar.

Hows that?  ^^V