i think the honor cap is a significant enough limiting factor in the acquisition of PvP gear. Rank decay just encourages you to put an unhealthy amount of time into grinding rank beyond the honor cap for fear of losing a good chunk of your progress every week.
If you're like me and you stop grinding when you hit the honor cap, your progress beyond rank 10 slows to a crawl. I lose roughly 1/5 of a bar of progress every week, which means the climb from rank 10 to rank 11 will take me a full month. I can only imagine what it will be like at higher ranks.