Even if you went 5, max dps tier 5, domination shards. it would still only be 7.5% dps flat increase. (Good, but not enough to matter IMO.) The pvp gear scales an entire tier. Effectively making it so you must have it to pvp because it scales into the next xpac.
Lets put it this way. If it scales from 252 up to 265, the stated 13 ilvls, your entire pvp set is greater ilvl than the stage six legendaries. (262 ilvl)
Do you like pvp’ing in gear that is better quality than legendaries? Because thats what the pvp gear is. Nobody can pvp without it given ilvl scaling.