My initial dislike of Special was due to it overloading our movepool with options I found to be "matchup fishy." Hemogoblin needs checks and the more strong moves it has the less mons are available that function as checks. Ergo, without moves like Boomburst and Fiery Dance keeping Special sets alive, general physical walls (Garganacl, Dondozo, Great Tusk) are much better checks to Hemogoblin.
Over time however it seems that Hemogoblin's pool of checks is still fairly limited. Anything that would like to switch into it faces one of two problems:
- Knock Off removing a key item like Leftovers or Heavy-Duty Boots, making the Pokemon more susceptible to chip damage and potentially losing the interaction over time.
- 252+ Atk Tera Ground Hemogoblin Tera Blast vs. 0 HP / 0 Def Heatran: 456-540 (141.1 - 167.1%) -- guaranteed OHKO
We can't do much about the second point as that's just part of playing Gen 9 and Tera Blast being universal. On the other hand, Knock Off is certainly an option for removal, and would mean that Hemogoblin doesn't have a "one size fits all" solution for various checks. Tera Blast still provides a way past certain Pokemon, but has much greater opportunity cost and lacks Knock Off's utility and long-term damage potential.
Of course, if we remove the designated fourth move slot on Hemogoblin, than another move will likely need to move into it's place. Hemogoblin uses Knock pretty selfishly, the team support aspects being a nice bonus on top, so the replacement move would likely be whatever is best at muscling through its pool of checks. Tera Blast puts in the most work here, granting a 120 BP coverage move and new typing to play around threats. I've only seen Ground at this point since it annihilates Heatran and is similarly good versus other Fire/Steel/Poison types (who knew Fairy/Fire/Ground was good coverage?), with some extra defensive utility in resisting incoming Poison/Rock move or neutralizing our own Ground weakness. I do envision people going this route with Hemogoblin more often with Knock gone, and it's more immediately threatening and game-swinging than Knock Off is, debatably making the mon more of a hassle to deal with. Being a Tera hog isn't ideal, however, and if Hemogoblin feels compelled to run Tera Ground, then there'll be less room for Tera Fairy in the metagame, which lowers the effective power of Extreme Speed. So in a roundabout way, removing Knock Off is sorta a nerf to Hemogoblin's ability to get away with boosting Extreme Speed to the ridiculous levels it can.
I definitely find nerfs which address Hemogoblin's bulk to be more attractive in this case. I argued before about how the combination of defenses + Extreme Speed + Bitter Blade + Bulk Up lets you live an absurd amount of interactions most other Pokemon wouldn't dream of.
A stat nerf is very appealing in my eyes because our moveset is honestly really cool, and it'd be a shame to lose that. I'd have to look into benchmarks more but lowering both defenses by a good chunk gets the job done. Our raw bulk is a bit over the bang average line IMO and could definitely see a harsh cut.
Replacing Bulk Up with a weaker alternative in Work Up or Curse is significantly more interesting. Bulk Up pulls a lot of weight thanks to the boost to Attack and Defense enhancing a lot of our kit. Bitter Blade especially enjoys the move, as hitting harder = more HP regained, and higher Defense = more efficient HP on the Physical side. With Work Up, we lose that Defense bonus, meaning Hemogoblin needs to rely solely on the Attack boost to get work done, and reduces the amount of power it gains from a free turn. Curse keeps the boosts, but lowers our Speed in the process. Hemogoblin is already quite slow, but still enjoys investing in Speed to outpace a handful of Pokemon in the Base 60 range. The Speed drop from Curse is enough to put us below Venomicon and Equilibra even with maximum investment, so by boosting our Physical stats, we in turn make ourselves more vulnerable to a lot of slower hard-hitters. The choice between either depends a lot on how much you value the synergy in our kit: I think both are equally valid.
Removing Bitter Blade is another option, probably my least favorite but no less effective. This move makes up for its average base power with the massive amount of healing you can get back from it, and largely allows Hemogoblin to get away with not having a Recovery move since a correct turn with Bitter Blade provides more than enough healing. Not having Bitter Blade means Hemogoblin needs to drop something if it wants better longevity or pair with a Wish/Healing Wish user. Don't worry about losing a strong Fire STAB in the process by the way: Fire Lash is an equally powerful move with arguably better damage output and good synergy alongside Extreme Speed.