Now that being said let's see if there are any options left to solve this problem. One way that has been suggested a lot of times in the past is to change Blunt Mastery and this would indeed be an easy way to deal with the amount of damage the Templar does. Yet this comes with a lot of problems. There are many way to change the skill itself, but it will have a big influence in game play so for the sake of it I'll try to make it understandable.
The first issue is of the so called "double dip" from both Magic & Melee boosting. This has always been part of the Templar and it should be removed! This because if you will take away the transfer from Magic towards Melee attack you'll encounter a few issue's. First issue is because of this transformation you prevent any Magic or Physical Defense to lower the amount of damage you deal. If you leave it towards Magic attack then Magic Defense will start to effect and you'll turn the Templar into a Wizard / Warlock / Rumir hit. If you leave it add Melee you first need to change the primary setting of the game that int provides Magic attack and not Melee attack. And after that they'll be the same as a Human / Avenger / Gaint / Noir and we have enough of those around already.

So the way to deal with it isn't to change the double affection, but to change the multiplier that has been added into the transformation. I'm not gonna explain or prove this, but thanks to some previous work of Iceyy I've been able to write a near exact formula to deal with it. The issue with this is that when you leave the multiplier to high it won't change anything for the OP Templars and if you leave it to low the people without the OP items aren't able to play the class anymore. There is a way around it and if GMs would be interested in it feel free to sent a message.

So now let's say the Templar class got fixed which changes will this bring towards the game. First of all the biggest damage dealers disappear. This means that the PvP is gonna last longer and it will be more difficult to kill anyone. This gives the classes with a healing skill more time to cast it and survive. The problem will appear if the healing will become greater then the amount of damage dealt in the same period of time. And trust me on the fact that if the Templars damage is cut into 3~5 this will be noticeable. How to overcome this problem would be to reduce the amount of Health players have. This is impossible, because if you go and figure out how the health of your character is build up you'll see that it's only from all additional of Items and not from the basic you have. So the only removable items would be all boosting scrolls (which has been tried for a very short period, but they re-added them because of all the asking for them.) the other way is to reduce the stats on the items. But this is unrealizable, once you start to change items or stats upon items you need to offer players to look upon something different or you'll lose your entire player base. So I won't consider this as a valid option.
Now let's say there is a correct way to reduce players health, then what will happen. The lower the amount of health the more burst are going to be effected. So when this will be the case it will result in a change in Dekans Skill as well. I know Skill Defense Armor & Marea's Battle are a huge downside for them already, but you can't ask everyone to play a priest with Skill Defense Armor just to survive against a Dekan. Then the issue comes from Guardians with Knight Symbol (this I consider less problematic as everything else since it requires a build up from Order Swing + Crazy Standing (makes you unable to move) + a lot of buffs (without any protection from debuff). Furthermore you'll have a problem with the Rear Blast from a Noir. The exact boost in this is yet unclear to me as I haven't tested this properly, but yet the damage is unaffected by any for of Damage Drop / Skill Defense. The same applies to the poison from a dhan.

Right so let's continue on our journey what happens next. The heals now will becomes overrated. So you would have to reduce all the healing skills in strength for every character. And not to mention you'll have to remove all the Teardrops and maybe even all the Legendary Health Potions.

After this comes the next problem, how you wanna stand against bosses when all damage is reduce. Boss in the world just gonna take more time so that's not so much of a problem. But how are you gonna be able to do Superior Dungeon stage 10-15. Many of you might not even been after stage 6 or if so just think back how much u used to pass there. And if you wonder why this is important you have to realize that this is the intended power level YNK this we had when it was first released. Nowadays with better items and all additional stuff I doubt anyone can say they're able to do it without any item from the Item Mall (This includes level 7 skills).

Alright so besides the reduction of a part of the Templar damage at the OP level I won't vote to reduce the damage to enhance the game play since it's just impossible due to all additions over the years. So let's see about enhancing the damage of other classes. Who will need a enhancement and how or why. Let's just take one example and leave the rest for later. I'll take out the Giants. They are probably one of the most underrated classes there are in game at this point. And the current solution wasn't the increase them, but they simply just gave the Savage a skill to play like a different class (mostly used the Templar). This doesn't solve the solution for the class itself, but it causes a huge issue when you wanna increase them. Now to fix them you would first have to add restrictions on which skills they are able to take away, yet leave the skill still be able to remove the buff as a debuff effect (this enhances the ability of a Savage very much in both group / 1 vs 1). Now after dealing with some issue's let's make a separation into group PvP and single.
For single target PvP I don't think the Savage needs much addition, because their ability to they to take opponents skills with a very short cooldown gives them a good chance victory.