* European bourses sag after Fed rally, bond yields tumble* Fed minutes show concerns about global economy, strong dollar* Dollar index slumps as U.S. rate hike expectations scaled back* Wall Street expected to dip as Q3 earnings get into gearBy Marc JonesLONDON, Oct 9 (Reuters) - A rally in world stocks sparked by Federal Reserve assurances it will not rush U.S. rate hikes ran out of steam on Thu