Hey there,
I’ve been playing Guardian in RBGs up to 1.800. Here’s what I do.
Talents
15 - Brambles
Gives a bit of damage reduction and most importantly a damage aura when you pop Barkskin. Absolutely necessary tool for defending flags.
25 - Renewal
Never really picked anything else. Don’t see the point in Wild Charge, as the moments where I want movement are usually the moments where I want to get away from enemies - not closer to them. Renewal on the other hand is another defensive cooldown that also synergizes well with Incarnation, Battlemaster trinket, Battle Standard and all the other HP boosting skills. Great for staying alive.
30 - Restoration Affinity
Usually Resto. Passive healing is another layer of defense, Vortex is a great defensive tool for when you are trying to get away from someone and being able to heal a bit is great in small skirmishes. When I’m defending carts on Mines, I pick Balance Affinity because you can do quite a lot with it while defending top cart.
35 - Mighty Bash
As a defensive option and to interrupt Convoke and stuff. Mass Entanglement when running flags to root the people who are hitting you.
40 - Incarnation
Another good defensive cooldown.
45 - Survival of the Fittest
The other two talents are poop and this one also synergizes well with the NOW legendary as well as the Brambles talent.
50 - Rend and Tear
All three feel kinda bad. Rend and Tear is the easiest to use, so I pick it.
Conduits
I’m Necrolord, so I play with Emeni as my soulbind. The two defensive conduits are Well-honed Instincts (auto-frenzy when you drop below 40%) and Layered Mane (xx% chance to apply two stacks of Ironfur). Could also go for Innate Resolve (15% more Frenzied Regeneration healing, which is an increase of about 5% of your max hp) or Tough as Bark (reduces Bark CD by 6s), but both feel a bit weak. Whereas a second stack of Ironfur (which I use a lot in flag carrying scenarions) seems like it scales way better in high pressure situation and would thus mitigate more damage. For Finesse conduits it’s pretty much the only two ones which aren’t bad: the CD reduction on Mighty Bash/Entanglement and the increased duration on Roar.
PvP Talents
Here I got two different setups: one defensive for flag carrying/base defending and one for being in team fights (I stay tank on temple f.e.).
Defensive
Demoralizing Roat, Raging Frenzy, Toughness
Teamfight
Demoralizing Roar, Roar of the Protector, Den Mother
Legendaries
As for Legendaries: you wan’t both. Sleeper and NOW. Sleeper for flag carrying, then NOW for flag defending. Sleeper for base defending, then swap to NOW while Sleeper is on CD, then swap back to Sleeper when it is off CD. I found that the way to loose a cart/flag is mostly because of CC rather than being killed.
Stats
I prefer: Versatility >> Mastery > Haste
Haste is nice if you are playing PvE where you can guarantee a smooth rotation, but in bursty/CC-heavy PvP situations I feel like having extra HP and healing is stronger and more reliable. But given the way PvP gear is statted, you end up with a lot of Haste anyways. But if I can choose, I choose Mastery over Haste.
To your item question: definitely go for the higher ilvl item. Even though Mastery stacks very poorly, it should be better in terms of defense in PvP. And you really want the extra stamina.