Pet gear wise, you have Plaguebearer of Dreeg and Nightshard Shield. Plaguebearer also converts upto 40% Pet vitality into Acid.
You can get -40% RR from it and also take Manticore devo to make up for the flat RR from Ghol.
Now, assuming that someone is not taking Plaguebearer and Nightshard, you actually end up with 10% more RR than you get with Ghol set (20% on Swarm + 10% from Pet).
But if you are/were using them, you end up with -30% RR and having to take Manticore/Bysmiel devotion, both of which are kind of sub par. The Bysmiel pet is too weak and a single source of RR & Manticore’s area of effect is weird with the cone thing.
However, it changes if you were or are using a Pet Cabalist instead of a Ritualist. There, you will be taking Manticore/Bysmiel anyway and you won’t have Devouring Swarm. So the only loss in RR is the 10% from the pet, which does not break the build or anything.
Blightfiends, for all their power, do not do well against Single targets in my experience. Perhaps there is something I have overlooked, but against superbosses, their kill time is much slower.
Their strength however, lies in that phenomenal AoE dmg they can output.
Now, with the loss of 1/4 of the pet, it is essentially a -25% total damage nerf. But there is also more, since Pets are also supposed to shield & tank for you and now you have one less body on the field.
As for their performance, this was my non Ghol BF build: ScareCrow - Pet Cabalist. But as you can see there, it borrows the power of Bysmiel’s Trinkets to get the damage in with the Blightfiends acting as fillers.
One of my issues with the change is that you can’t even use the Medal alongside any other Pet Set other than Lost Souls (which has problems of its own) or… Diviner’s.
But at the same time, you don’t really have a reason to pair those sets with Blightfiends unless you want variety for the sake of variety.
Unless the options presented are equally strong, people will prefer the stronger ones and hence why personally I believe that forcing “variety” upon the players is a bad move, especially if it is done by taking away their stronger option(s) so that they are left with a number of weaker choices.
Now, @thepowerofmediocrity made this post regarding Pets and their Reliance on Sets. That is indeed an old thread and there have been numerous changes since then, but I would say that most of the core issue still remains in that most of the power comes from the set bonuses or individual items that make up the set even if you aren’t going for the full set bonus.
So, when you decouple Blightfiends from their dedicated Set, either you will be using them to support another Pet you are focusing on (like a Vitality Diviner Reap Spirit Ritualist) or you will need to find parts from different items to make up for the loss of set bonuses.
Can it be done? Yes.
Will it be fun to play? Sure.
Will it be able to compete with a build using a dedicated set and is not a meme-y one? I’d go with “No” and hope I will be proven wrong.
Now, there was a time when I judged a particular something in a patch rather harshly only to end up being completely wrong about it.
Enter: Gate to many worlds
It was a time when Cataclysm’s Eye lost its +1 to skills which was moved to Set bonus. I was naturally not happy with the change and it affects most of my builds even now, due to losing that +1 to skills.
And I was rather condemning of Gate off-hand as even though it was a Pet item and provided new pet(s), it was for some reason focused on Arcanist, pets had no way to benefit from flat dmg etc…
Then it ended up tremendously boosting the damage of my Fluffy Squishy that it ended up taking the place of Off-hand instead of Cat’s Eye and now, even if Cat’s Eye were to get its +1 to skills back, I would still be keeping Gate.
But unfortunately, nothing new was provided to Blightfiends to help make up for the loss of the Set if you wanted to take up Unstable Anomaly. That is what I take more of an issue with than the loss of the set bonuses.