If you had a good group I don't see any reason a I65 group couldn't down Garuda EX. You would need a setup which used none of the same jobs, especially for the WAR with added DPS and the faster limit gauge. But as I have been gearing my other classes I have noticed that an I65 rating can have say an I80/90 weapon and some DL/ Old AK gear mix (like Peltgast, Hoplite, etc.) The reason I see people fail even with I90 is because they just aren't very good players.