But seriously, I've gone back and forth on this topic. I'd rather dry hop after I dump the yeast (in the fermenter) but only because I don't want 5 ounces of hops taking up space in my keg which could be filled with beer. I typically blow through my IPAs at twice the rate of other brews.
The counterbalance to this is that I am always surprised at the amount of yeast left in the fermenter after I dump the yeast. So I'm not sure what I am accomplishing by dumping prior to dry hopping. It seems self evident that the yeast much below the surface of the yeast cake doesn't get much contact with hops. So if it is only the top (1/4 inch?) of the yeast cake that can interact with the hops and do the dreaded bio-transformation, the yeast left after dumping is just less thick - not absent.
Regardless, unless and until I learn of a better way, I'll continue doing what I do: Cold crash (Just 20* or so, not down to freezing. I just want to signal the yeast to go to sleep and precipitate out.), Dump the yeast until beer comes out, dry hop for two days at 65*, and keg. This seems to work for me - I like the beer - but maybe it could be better...