I would say chaining the monsters is the fastest, but only time I have done this is when theres has been 2 whm's in a party, and 1 whm constantly heals the tank while the other heals the rest of the party.
But to do this you have to be quick and know what you are doing, I got into a party who wanted to chain lizzys and I got from lvl 12 to 14 in about an hour but you do need 6 people who know their jobs otherwise it will just be a massacre.