I would go for an alternate approach here, dropping a few things and adding to your increased damage output.
http://db.vanillagaming.org/?talent#LMGhbhbZcZxfts00dio 17/3/31 Impale PVP Spec.
Shield Wall or Armor:
Let's first tackle your "more armor over imp shield wall" debate. Assuming you are doing battlegrounds, different times recklessness is better, other times shield wall will own the day stacked with last stand and a life-giving gem.
If your group is charging into an already established group of the opposite faction (you should be lead guy), pop the 3 above for 12k+ HP and 75% damage reduction for 15 seconds. You charge/intercept right into the heart of their group and pop a fear. If you didn't have their attention, (as they normally are still trying to target healers or CC raged dps) they are after you now cause you made the center of their attack weak. But guess what, no matter how hard and how many burst you, you are still up. Now with your team no longer focused, they fearlessly follow behind and start picking off people as you continue to run as far into their group pushing them back. Get to the healer line, shield bash one to silence them, concusive blow another to stun that heal as well. Hit them with a shield slam, it can crit with the correct gear which I will mention over 1.4k (i've gotten a 1.5k so far). + a 400-600 white hit. While everybody have been trying to hit you, revenge will always be up and have 45% chance to also stun the healer again. This puts the healer that you had stunned under much stress, healers are now trying to heal themselves not the DPS that your group is now freely picking off.
By this time a pally or priest will be on your back and your cooldowns are worn off. You should use shield bash on healer again ASAP to silence again. Usually even though your cooldowns are now off, the dumb group you raged and feared gives up on even trying to kill you as they were doing NOTHING to you. So they then panic and go for a "squishy". At this point you are not as tanky, but not being focused as they still think you are too hard to kill and not worth it. Roam the battlefield and go big shield slams, overpower melee and hamstring. Use concusive blow on casters, shield slam on leather or lower.
^ 30 min CD? Yes, but this turn of events at the start of a battle ground instantly gives your team the advantage to get an early lead. And that is what it is about, winning.
TL;DR: 50% longer shield wall > 4% more armor. Melee will struggle to hit you anyways due to the def gear you will have that comes from stam / block value stacking, you take most damage from casters, so this is null even more so.
Imp disarm
This talent is only for half the enemy you will come across, and a majority of those that you would want to disarm.... immune. Weapon chains, or rogue gloves. waste of 3 points and is expensive to use. Better off using that rage for a concusive blow / shield slam combo.
Imp Overpower
The gear you will be wearing will be lacking the crit usual pvp gearing has, which means more chances for this to crit. Why not make it crit and make those rogues / huntards trying to avoid damage.
Impale
This is where your PVP effectiveness comes into play. Big shieldslam crits, much better overpowers and white hit crits.
3/5 Cruelty
You lose 2% crit here at the cost of making your crits 20% stronger. Is it worth it? Yes. You can get crit from gear/buffs, can't get crit damage from anything but this talent.
Gear:
PVP you naturally STAM stack. Next stat prio is Shield Block Value. Then Agil & Crit. This gives you big shield slam crits the talent build is setup for. Styleens, 3/8 T1, T2 shoulders, T2 boots. ZG helm / leg enchants. Fill in your other pieces with as much crit/agil w/o losing stam. Naxx endgame, I've popped shieldslam crits using Sapp trinket for 2.2k - 2.4k - nasty.
Helm: Field Marshal's Plate Helm
http://db.vanillagaming.org/?item=16478 + ZG Enchant 10 stam / 7 def / 15 block value
Shoulders: Pauldrons of Wrath:
http://db.vanillagaming.org/?item=16961 +5 all resist enchant (has block value)
Chest: Field Marshal's Plate Armor
http://db.vanillagaming.org/?item=16477 + 100 HP (2/6 PVP set for +20 stam and 3/6 set for -5 sec on intercept)
Bracer:Bracers of Might :
http://db.vanillagaming.org/?item=16861 + 9 Stam
Gloves: Gauntlets of Might:
http://db.vanillagaming.org/?item=16863 + 7 Agil
Belt: Belt of Might:
http://db.vanillagaming.org/?item=16864 (gives 3/8 T1 for 30 block value)
Legs: Marshal's Plate Leggaurds :
http://db.vanillagaming.org/?item=16479 + ZG Enchant 10 stam / 7 def/ 15 block value
Boots: Sabatons of Wrath :
http://db.vanillagaming.org/?item=16965 + minor speed increase (has block value)
Cloak: Eskhandar's Pelt :
http://db.vanillagaming.org/?item=17075 + 5 all resist (10+ all matched with shoulders) / Dragon's Blood Cape
http://db.vanillagaming.org/?item=17107 alternate for stam stacking.
Neck: Master Dragonslayer's Medallion
http://db.vanillagaming.org/?item=19383Ring1: Archimtiros' Ring of Reckoning
http://db.vanillagaming.org/?item=19376Ring2: Don Julio's Band
http://db.vanillagaming.org/?item=19325 (This is your 3% hit cap for PVP)
Trinket1: Lifegiving Gem
http://db.vanillagaming.org/?item=19341 when on CD and you are out of combat swap to: Insignia of the Alliance
http://db.vanillagaming.org/?item=18854Trinket2: Styleen's Impeding Scarab
http://db.vanillagaming.org/?item=19431 (has block value)
Weapon: Thunderfury, Blessed Blade of the Windseeker
http://db.vanillagaming.org/?item=19019 / Vis'kag the Bloodletter
http://db.vanillagaming.org/?item=17075 - Weapon-chain isn't need as much as most of your damage is from shield slam, ability to silence from shield bash. You will also be low prio on a disarm. 15 agil may be your best enchant to get more shield slam crits which the tanky gear lacks.
Shield:Elementium Reinforced Bulwark
http://db.vanillagaming.org/?item=17075 +7 stam (has block value on it)
Ranged: Blastershot Launcher
http://db.vanillagaming.org/?item=17072