3) The PVP Defense relics are very good, but I would caution against using 2 of them. The Elite War Hero relics lose 51 endurance to the DG relics and take away a soft cooldown.
I don't put much stock in Endurance whatsoever, especially for Guard/Juggs and VG/PTs so the "loss" of 51 Endurance means almost nothing to me.
The only thing that would have an appreciable effect would be the loss of the soft CD which is, honestly, isn't a major of a concern as you might think: you *should* have Saber Ward and Warding Call both up and available for each of your sub-60% tank turns and Enure for the last if you get it. If you need more than 2 full tank phases on each tank for sub 60%, you're pretty much screwed anyways so you shouldn't absolutely need the "extra" CD: NiM Kephess on 8m has 1288301 hp; 60% hp is ~773k; each DPS should be doing at least 1900 DPS and tanks should be dealing 700 DPS while they aren't affected by Breath of the Masters, which totals to 8300 ops wide DPS (4 * 1900 + 700); the TTK for Kephess sub-60 should then be slightly less than 93 seconds (should be some rollover DPS from DoTs at the pushover); each Breath of the Masters cycle takes 20 seconds; 93 / 20 = 4 cycles with a 13 second overlap, which is short enough to ride Enure (or just kite him).