Besides Woosa innate protections, survivability, and high skill damage, she has AP on her passives, -15 magic dr, -20 dp, trivial T3 add-on access, and constant summon damage.

This makes her incomparibly strong at certain gear levels relative to other classes. I noticed the 10 melee AP buff at dehkia thornwood. I think that the value on the buff should be increased to at least 20 and perhaps even reducing the melee damage reduction of thornwood mobs. I would like to grind thornwood on other classes but it's sad that woosa is just way too good to consider that. 

I know I know, just grind on the class you want w/o caring for efficiency. I do that at every other spot in the game. It's just that for the high-risk, high-reward dekhia spots, there is absolutely no reason to bring another class, especially near the entry levels of gear for those spots. The difference in performance is staggering as well as the increased risk for classes w/o the insane regen and protections of Succession Woosa.

Please, if you don't want to give melee classes general PVE buffs, just tune the melee ap buff and melee dr numbers for Dehkia Thornwood, or dehkia spots in general

Huge agree. I don't think that per se the ap/dp passive stats are the issue because that is directly a gear-problem in terms of solving.
The problem is that woosa is so perfectly tailored to these spots in how she fights, AND has the coveted triple stack of -(type)DR, -(skill innate)DR, and then -(addon)DR, it's like it was made for her and nobody else.

Normally the difference between a good and bad class at a spot is like 20-30%. That's pretty bad but here, Woosa literally double or triples the effectiveness of many other, even considered top tier classes. Why? Nerf it in line with other grind spot incomes, or change it so that one class is not head neck shoulders and torso above every other kind of combat style.

You describe exactly why we have such a large discrepancy between classes in Dehkia!

At Thornwood, the initial AP requirement is set at 867 AP (where you only receive 5% of your AP), and from 867-1000 AP, you receive 100% of your AP, which is excessively high. With typical end-game gear, players have around 950 total AP, resulting in only 120-150 effective AP.

If your class has a passive AP and a DP debuff, this difference becomes even more obvious compared to the standard classes.

Unlimited FG and good HP recovery are the cherry on top for Woosa.

My suggestion would be to lower the inital AP requirement to around 500 AP and just make the spot difficult like Crypt of Resting Thoughts.

Yeah they should nerf woosa, she is overperfoming on every endgame spot.

Thats why Dekhia Spots are such garbage to be honest, not exactly sure what PA was thinking.

Regarding Woosa, well, that goes to show PA balance levels.

In my personal opinion, having high cap areas where people actually need to progress and gear up to go there is a good thing and something BDO was lacking for a good while. I definitely advocate against reducing the requirements, especially since that would bring up a lot more balancing concerns than even in the current state.

However, the current performance of classes in endgame PvE is again diverging by far too much, lead by Succ Woosa at the very top. Recent efforts to buff lower performing classes and balance PvE among all classes were somewhat fruitful, but have been negated by further buffs, gear changes and new spot mechanics / requirements. PA really needs to take another look at what makes the top performers perform so well, and either nerf the outliers, or buff those at the bottom until the PvE performance especially in endgame is more equalised

Can someone explain me why? 

My problem with these high inital AP spots is, that AP scales exponentialy instead of linear. Same with classes, already strong PvE classes accel way better than bad PvE classes. It's the same problem back in the day in Elvia Serendia, when you did drop more Weapons the faster you clear which made already good grinders broken there!

Why do we gatekeep the spots behind these high AP requirements, when PA can design spots like Crypt of Resting Thoughts where the mobs are strong but has normal inital AP (around 500 AP)?

Because people need goals to move towards. And high requirements = goals. Same reason you also want to technically increase the rewards depending on requirements, in order to force players to move on and dont cause congestion in other spots for the lower geared players that just got the entry to that spot. If the spot was a 500 AP requirement, well then it only should make the money of a 500 AP spot, aka like less than half of what it makes right now. 

Having spots with high requirements is good from a progression perspective. 

Also, if you move the requirements to 500 AP, you will simply get the balance issue at 500 AP instead. Maybe it will balance out on the top end, but at the low end, the better grinders will still profit by far. We already have that exact issue with orcs, where requirements were lowered. Now a season maegu can grind better there than a 280 AP char of another class. Moving the goalpost for these requirements does not solve the balance problem. It simply causes crowded spots, worse outcomes and lack of goal setting for progression, all the while keeping the very same balance issues, just at a different level of gear.

Thats why changing spot mechanics or requirements does not work. If its 2 or 3 classes that excel at a spot out of the norm, then the classes need to be adjusted.

Yes, I fully agree with the first part. We need spots which require alot of gear to grind, to give players which hit softcap to keep going.

An initial AP requirement of 500 does not mean that the spot only needs that much AP to be grindable! Here for example Crypt: