Basically we are back to the old system where better gear means you have an advantage. And the advantage can be staggering.
For example, I have ilvl 401 and just fought against a DK in a random BG who had ilvl 425. I had 207,000 health, he had 302,000 health. I managed to remove 23% of his health before he killed me. We fought about 8 times, and that was the best result. As a moonkin, I had 2nd highest damage done in the BG at 1.9 million, and he had the highest at 6 million. The match was SSM.
If that doesn’t give you perspective on how important gear is, nothing will. I don’t care what everyone is spouting about scaling and whatnot; basically raid, or die. That seems to be Blizzards philosophy to being competitive in PvP.
Nothing you gain from random play will come even near open world PvE event gear.