Its not worth it.
Over the course of the fight, you should be taking the bulk of your damage from rag himself. Thus 1% of the bulk of your damage is almost always more than 2% of the damage taken via spells during specific times in the encounter. If your finding yourself in need of some addition survivability during certian abilities, try working out a cd rotation before the fight starts. If you know you NEED the 25% magic damage reduction at roughly 6:30 seconds into the fight, build your rotation around that time interval. Perhaps using your lesser cds, such as trinkets, would be a wise idea.
PS- hard to give advise based on your armory when your in lvl 70 gear
Reev: So, do I macro /dance into Shield Slam now? Raysere: Yes, I hear it increases your DPS Gold balance gear quality attractiveness to the opposite gender considerably