I am quite an experienced player of DD5, and I feel that trying to bring a darker settings to this game is an excellent thing. Forgotten Realms are really high magic and not Sword and Sorcery like.
For example your Corruption rules seem an excellent idea to decrease the power of magic.
But I have a concern regarding the 2 rules that I see in your v2.0 that give a character the possibility to have a permanent Advantage, or Disadvantage.
I mean the Goblin Dodge as a bonus action, without cost, and the Scoundrel Advantage from Monster Hunter.
Maybe this issue has already been adressed, so sorry for not having read all the forum in such a case.
This benefits are huge for the characters, corresponding more or less to a permanent +5 to D20 rolls (or -5 for the opponent in case of Dodge), and tend to unbalance the game as I experienced it in Adventures in Middle Earth, another OGL License where some fighters could have a permanent Advantage due to their origin. This fighter just ended up eclipsing all other characters in combat. We just had to protect ourselves and wait he killed everyone.
What makes the strength of DD5 is that all races, all classes have a way to shine in almost any situation. Everybody is having fun.
Giving Advantage always come with a drawback in DD5, for example it lasts only 1 minute (Paladin) once per Long Rest, or it gives Advantage to your opponent also (Barbarian).
I am afraid these 2 rules will give the Goblin Scoundrel an overpower feeling, boring to other players.
If the Goblin can Dodge at the cost of having Disadvantage to his next attack for example, or the Scoundrel gain Advantage against Large monsters for 1 minute once per Long Rest, that comes with a cost similar to the Corruption for spell casters. The player has to decide when to use it or not. Make it automatic, then it becomes too powerful, at least that's what I experienced.
Thanks for the work anyway, I am sure it will be a big success.