Given how much weaker Ret is outside of CDs compared to other classes and how its high visibility pretty much guarantees you will be shut down when you cast it, Avenging Wrath really should be 2 min baseline.
Retribution's PVP 4 pc bonus needs to be changed to "You maintain at least 1 Holy Power at all times."
Ret's problem is sustained. This can be attributed to several reasons, but in a PVP setting a large part of this is because you must first build up to cast Inquisition. The damage dealt while generating those first 3 Holy Power is already needlessly gimped.
So you get those 3 Holy Power and cast Inquisition. Now you must build back up to at least 3 Holy Power again before you can even consider Templar's Verdict, but because of the inherent cooldowns of our Holy Power generators and Ret's history of struggling to reach their target, this will take some time.
By the time you are able to generate the necessary Holy Power, there's a very good chance that you will not be within melee range of your target. Kiting, stuns, fears, etc ensure that the majority of the duration of Inquisition will have been spent in pursuit of the target. So by the time a Ret is finally able to get within melee range of their target, Holy Power will most likely have to be spent on Inquisition again instead of Templar's Verdict.
To further compound the issue, Inquisition is also necessary for survival, as the additional 10% crit affects our heals as well.
In short, a PVP setting punishes the current Ret mechanics because Ret's damage and survival are gimped by Ret's need to buff their damage and survival.
Changing the PVP 4 pc bonus to allowing Ret to maintain at least 1 Holy Power helps PVP Ret in multiple ways.
Having that constant 1 Holy Power alleviates a lot of the punishment of having to maintain Inquisition. Inquisition fell off during a CC? You will now always have at least 1 Holy Power to get the buff back up and running so those first 3 HP generators aren't needlessly gimped. Even if you had 3 HP, casting Inquisition would still leave you with 1 HP to assist in getting back to what it is that Ret is supposed to do, which brings me to my next point.
This also means more frequent access to Templar's Verdict. More frequent access to Templar's Verdict is a BUFF TO SUSTAINED DAMAGE.
In addition to Templar's Verdict, this would give more frequent access to Word of Glory. Given Ret's dependence on Divine Shield for survival and the fact that it can be removed by 2 of the most dominant classes, Rets are easily trained. More Word of Glory casts would at least help to delay the inevitable.
A counterpoint to Word of Glory, however, would be the need to give WoG the TV treatment. Unless WoG were only able to be cast with 3 HP, a constant 1 HP could be abused by spamming 1 HP WoGs, which could be further abused when coupled with Divine Purpose.
And finally, though least important imo, this would make Pursuit of Justice a more enticing option for those Paladins who can't Holy Shock themselves to a higher run speed.