From some "inside" experiance:
The Dunlop Rover RVXT is a good tire, from a price point to a functionality standpoint.
Great grip, quite ride, and a severe winter service rating like the BF Goodrich AT KO.
The only problem as mentioned is the balancing issue. I have not personally crossed it but some online forums (ie tire rack) note that some GY Assurance Comfort Treads also have a potential balancing issue.
As far as getting some one to do a warranty adjustment technically any dealer of GY should honor that. It comes down to how aggressive you are, who you talk to, and even who you know in the Tire business. Any one can do a warranty adjustment if the WANT to. The key is weather or not there is any $$$ in it for the local shop to do that for you. For example you have better chance of getting them to give you a $ adjustment of you have 25% wear left. That means they would gladly sell you a new set of tires minus the $ adjustment. All the shop is thinking about are the profit margins for tire balancing, alignments, valve stems and road hazard $ to be gained by you.
Sad situation is it not? It sounds as if Tire rack needs to strenghten its relationship with local vendors to make tire warranty adjustments less of PIA for the consumer.
My .02$ worth.