remember ragnaros is balanced to be 1/2 a tier harder so has 1/2 a tier of ilevel requirement higher (6ilevels) if your stil sporting a few t11 normals it's probably beyond you until you cut that down to only 1/2 items that are lower than firelands quality.
firelands normal is 'balanced' for 359's to be ableto do the first 4 after those the ilevel/difficuly goes up and it could be argued that ragnaros normal is (like his loot) 6ilevels higher so you need 365's avg at least to do him on everyone. especialy tanks/healers.