Divine Sacr:
Use it with bubble --> 30% less raid dmg, it will last it's entire duration. You get no dmg done.
Use it without bubble no raid dmg --> your tank takes 30% less dmg, but that 30% is redirected to you, stops at 205 of your hp or when it's done ...% your health pool.
Use it without bubble raid dmg --> you're gimped.
Use it with bubble (improved divine sarcifice --> divine gaurdian) --> your raid takes 50% less dmg, after 6 to 10 seconds the raid takes 30% less dmg.
If you have improved divine sacrifice (--> divine gaurdian) -->
Macro: /cast Divine Sacrifice
/cancelaura Divine Sacrifice
your raid no takes 20% less dmg and the damage vanishes in the air.
THAT is all :P