Post-DLC most GS lords are in a pretty decent spot with the outlier being Grimgor. Although due to the knockdown changes he can now stand and fight the enemy, he still has all the same problems he always had which is that he has no real ability to pick engagements and ends up fighting chaff all game. And now that the Waaagh! has been made a faction mechanic rather than a lord ability he no longer even plays the role of Waaaagh battery.
Below is my thinking behind why he is still bad, and what can be done to help him:
Abilities only target lords/heroes
A big issue he has is that 2 of his abilities (Best of Da Best & You're next) only work on enemy characters which means that he still can't meaningfully fight large non-character monsters. There is never a situation where Skarsnik would not be a better choice as he is just as tanky, has better abilities for combating large targets (be they lord/hero or just a monster or cav unit), can give AOE buffs and realistically Grimgor can't get to the targets he wants to fight anyway.
Lack of mobility
Grimgor still suffers from not being able to fight the target he needs to make his cost back (or at least attempt to). Blood-Forged Armour in theory should be able to assist him getting out of chaff and to the enemy he needs to fight, but as a 200+ gold explosion ability (with some extra armour) this puts his cost up even further and makes it harder to get his value back. This wouldn't be such an issue on roster like the Dwarfs where you can park Ungrim (who has similar issues) next to a Thunderer or Trollhammer and your opponent will have to come to you to shut it down. As a primarily rush faction, Greenskins need to go to their opponent and can't threaten enough at range to draw the enemy to their fighty lords.
Not really very tanky
Grimgor has 4k hp and 120 armour so seems tanky on paper, but he has 45 MD and any chip damage he takes really hurts him. Especially once he starts to get exhausted and his armour goes down to 90.
Option 1: + Perfect Vigour. This would make thematic sense and improve his mobility and tankiness throughout the game.
Option 2: Bloodforged armour price reduction. Make this a 70ish gold ability so Grimgor has a hope of blasting his way to a target that matters.
Option 3: Make You're Next an ability that can target any unit, not just lords/heroes.
Be interested in other recommendations or suggestions.
TL;DR: Never a good reason to tank Grimgor over Skarsnik because 2 of Grimgor's key abilities only target lords/heroes and he lacks mobility to make an impact. GS also can't threaten enemy enough at range to draw enemy to fight Grimgor.