SO I ran four (almost five) different Hound runs last night and noticed a change. In groups I have been in the standard method has been to send an intimitank after the dogs in the center with some clerics to keep him up and then have roamers travel the outside, one person pick up the first three stones and goes in and charms the puppies. Then someone else grabs the next three stones and when they are obtained everyone goes to the middle.
Well last night the third portal did not have two flayers as usual it only had one and in fact only 4 stones were immediately available and it seemed to me that more were not offered until after beholders had spawned. However it wasn't that bad since the dogs seemed to take Xyzzy down faster than normal. Personally I don't think this is going to change how this quest is run but it is worth noting so no one wastes time looking for that 5th and 6th stone.