No real need for secondary in my opinion. It makes less of a mess in your primary to split up the dry hops and yeast cake and you may lose less beer in transfers, but other than that I'm not sure of the thinking behind having to use a secondary for dry hopping.
I've done it both ways now and the only difference has been that with the dry-hopped primary I got more yeast sediment in the bottles, but that might not have much to do with anything, as I didn't give it much of a chance to settle after moving it to the bottling area.
I would say that 2 weeks is on the longer end of dry hopping, and if you are putting more than 1-1.5oz in there you might get some grassy notes, some say.
Are you using pellets or whole hops? Either way, don't use a bag and you don't need to stir, they will find their own path to the beer. A swirl of the whole fermenter by picking it up and spinning wouldn't hurt, but they'll all get there.