Hi everyone.
This post is made after some news about week 4 PTS damage output reported from player to Zos.
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General Dragonknight Class Balance & Power [Feedback]: We are continuing to monitor your feedback following the latest Dragonknight class refresh update we shared
here. We have seen some reports that Dragonknight damage output seems to have gone down between PTS Week 3 and PTS Week 4. We are seeing the same thing on our end, and are digging into it. Thank you, again, to everyone who has contributed bug reports, feedback, and the discussions during this PTS cycle. We greatly appreciate your collaboration.
First, I would like to give credit to Skinny Cheeks video made yesterday, video that made me want to do this post, for players, and for Zos, that trying to explain some points about how the game calculate output damages in PVE content, specially in endgame scored PVE content.
This type of explanations was surely made on others media like discord and maybe on an old thread (or the Skinny Cheeks video itself), but with recent DK changes on the pts i would like to refresh this point. That said, as Skinny said, "the following is pretty common knowledge for people in endgame like theory crafting", runing into hard mode trials or working on hard achievements.
So i apologizes if this post is repetitive and redundant.
- So lets explain end one way how damages are calculated. i precise that explanation concern only damage done by a player to a monster.
There are 2 multiplicative brackets, independant and separeted used to apply a bonus to a damage. First is damage_done, and applied on PVP and PVE, the other is damage_done_to_monsters, which is applied only against monsters.
Simply, the formula looks like this : 
I also put forward the hypothesis that exists an other bracket for damage_done_to_players, like it's mentioned on Marksman's Crest 5pc bonus and Languor of Peryite 5pc bonus...
So the fact is each bonus in the SAME BRACKET is not multiplicative, IT'S ADDITIVE
For Damage_done there is bonus like slayer, vulnerability (its a debuff but works exactly the same), berserk, and others. For Damage_done_to_monsters there is Velothi, Ansuul and others...
So the detailled formula, with explained brackets, looks like this : 
Its simple to see that damage_done bracket have much more bonuses than the damage_done_to_monsters bracket.
The result is :
If you apply a new bonus on a set, spell, etc, it will be greatly more valuable to put this bonus in the damage_done_to_monsters bucket because it's closer than the actual percent that you'll see in the tooltip. The damage_done bonuses are much more diluted with others, so the real bonus applied is even more lower than the bonus mentioned in the tooltip.
- Now what Zos did in Week 3 and week 4 with the Dragonknight
In Week 3 patch note :
- Flame Lash: This morph now also grants 12% damage done to monsters for 30s after activating if you are a Dragonknight.
In a future PTS update this will be increased to 15% for 45s but only if all stacks are consumed – to help avoid turning it into a passive buff effect and more of a reward for using the ability to its maximum effect.
- Molten Whip: This morph now grants 5% damage done against monsters per stack, rather than 85-100 Weapon and Spell Damage. This effect only activates if you are a Dragonknight. Seething Fury no longer generates stacks if you have Engulfing Dragonfire slotted on either bar.
What has been done in week 3 is adding a 12-15% bonus in the damage_done_to_monsters bracket by using/sloting Flame Lash or Molten Whip as a dragonknight.
Now in Week 4 :
- Flame Lash: This morph now grants 7% damage done, doubling against monsters, for 45s after spending all stacks of Power Lash, rather than granting 12% damage done to monsters for 30s after gaining any stacks of Power Lash. The healing from both versions now always activates, rather than requiring you to deal damage.
- Molten Whip: Seething Fury now grants 5% damage done to monsters and 2% damage done to players per stack, rather than only grating 5% damage done to monsters per stack. Seething Fury is no longer deactivated while Engulfing Dragonfire is slotted.
That Zos want to do is applying the Flame Lash and Molten Whip damage bonus also against monsters and agains players, but with a lower value against players.
BUT, what was actually done is changing the bracket in which the bonus is into the damage_done bracket, but with a lower value against player.
This actually adds a bonus against player, but decreases so much the bonus against monsters, for reason i explain before.
The following is just an example of the impact of the changes, i put random value in a raw direct single damage done by a DK player to a monster with Hunstman warmask and Tideborn and Flame lash or Molten whip 15% bonus. Most of bonues in the damage_done bracket are applied, as it's supposed to be on an organised endgame PVE Roster, or against the 21M dummy.

- What't next ?
Now we have seen the problem.
The most simple is to undo the Week 4 changes. The damage output of the dragonknight would be the same with no nerf in PVE content, but with no up in PVP.
But, the good solution in my opinion is to divide the bonus of theses spells into both brackets. To retain the global 15% bonus against monsters with adding damage_done bonus of 7% (for PVP content), you could put a damage_done_to_monsters bonus to 10%, additional to the 7% damage_done bonus. This will remain almost the same final value.

This is the end of this post. I hope this will not be useless, for players, for Zos developers or community managers feedback.
I wish you all a good game, and thank you to those who had the patience to read everything.