This may be controversial here but the following small post is my defense of the current way Retaliation can function.
Traits
30 Valor – Purity, Strength of the Fallen, Altruistic Healing
30 Honor – Writ of Exaltation, Writ of the Merciful, Superior Aria
10 Virtues – Vengeful
Gear – Full power/toughness/vitality. Weapons – Hammer/Greatsword
Utilities – Signet of Resolve, Stand your Ground, Hold the Line, Signet of Judgement.
So, heres how it goes.
Open with 3x Hammer swing basic attack for Protection symbol, use Hammer Mighty Blow for Retaliation, use Stand your ground for more retaliation, do 3x more Hammer swings for another Protection symbol, switch to Greatsword and use leap of faith through the combo field to gain more retaliation, use Symbol of wrath for more retaliation, use Blinding blade for the DoT then use Whirling Wrath. Swap back to Hammer and repeat the entire combo. You could even switch to Greatsword after the first 3x hammer swing/Mighty Blow, and leap seeing as though Retaliation stacks duration.
And thats how Guardian achieves the second highest PbAoE damage currently ingame, second currently only to warrior. Please note that this is intended for PvE.
Thats my small defense of the current way that Guardian can function in PvE with Retaliation up 100% of the time and Protection up about 70% of the time. Nerfing Retaliation would be a huge mistake and would basically destroy this Guardian build which is perhaps the most useful PvE build currently available for the class.
Note: For many situations in PvE you can swap out a utility of your choice for Wall of Reflection, which is an extremely powerful spell in many PvE situations
Now, thats all fine and dandy but you may now intervene and state that a major issue with Retaliation comes in when we talk about PvE/PvP balancing. Firstly, i think GW2 should separat PvE from PvP like they did in GW1, that way you can balance classes in PvP without damaging them in PvE or vice versa. In tournament PvP Guardian Bunker builds have been proving extremely powerful due to large amounts of retaliation + protection, however, i think this is only the case because optimal arena class + combinations have not yet manifested. There is no need to tamper with Retaliation and hurt PvE just because people have not figured out Tournament pvp tactics and what class build can be used to counterclass another. For example, if a 5 man Tournament team had a Thief built for boon removal and player harassment, it could be used to counter around 60% – 70% of the damage output of a bunker Retaliation Guardian by using Sword/Dagger and 20 Trickery (+ a Mesmer with Null Field ripping boons would be insane) while the other players in his team get to work on the other enemies. Simply put, destroying an amazing PvE build just because people in Tourneys cannot figure out tactics and counterclassing is not the way to go.
At this point you may be thinking what about WvW? Bunker Guardians are very powerful in WvW. My response would be again people should learn tactics and counterclasses, and here I would also add that WvW is inherently chaotic, unstructured and in many ways inherently unbalanced because people run around in different gear and enter at different levels with not all utilities unlocked, the server with the highest population almost always wins, people form huge zergs where class balancing has very little meaning whatsoever etc. WvW cannot be used in any way to try and figure out class balancing. As for Spvp, my same comments for Tourneys still stand.
If Retaliation still proves too much of an issue for you arenanet you should simply buff boon removal amongst some of the other classes. Guardian is one of the strongest, if not the strongest PvE dungeon class at the moment, you should not be looking to damage its most amazing PvE tank retaliation builds. You should be looking to add improvements to some of the other classes which need it.