I am the Scientist now
This post displays a relative lack of knowledge with respect to the current format. Choice Band Weavile generally does not see significant use (22% in OU, which has more CB usage than CAP due to Arghonaut making Weavile generally require more longevity). It absolutely is a strength in a design sort of speaking as it allows us an additional factor to design around.252 Atk Choice Band Weavile Knock Off vs. 0 HP / 0 Def Victini: 302-356 (88.5 - 104.3%) -- 31.3% chance to OHKO
That calc is with Victini holding an unknockable Firium Z, so Knock is at 65 power. People are seriously overestimating Fire/Psychic's abilities to take weakened Knock Offs. Arguing that 30i being weak to Knock Off is a strength bEcAuSe FiLtEr is absolutely baffling.
We could work around Knock Off or Stealth Rock if it was just one of them. But not both. That Victini calc is a guaranteed OHKO if rocks are up.
While Fire/Psychic has some defensive merits, let's not pretend the ability to take K-Off's is one of them. I personally think Fire/Psychic is terrible.
Edit the larger thing is that Pex Knock does legitimately 0 to most appropriate bulk spreads, as does stuff like Clef Knock.
Beyond the point this lets us change a losing pressure matchup into a winning pressure matchup, which is fairly important for how the mon plays in a match.
The implicit assumption in the above calc is that because a hypothetical 100/100 Fire/Psychic does not take the single strongest physical dark move in the tier, there is no point in using our item to reduce a SE Knock's damage. This is what I am challenging by pointing out that using our orb to reduce a SE knock's damage is worth it, by instead talking about HDB weavile, which is very achievable to live (thus changing a losing pressure matchup into a winning pressure matchup). This further would allow us to take weaker Knock Offs very easily, despite them being SE, giving our Fire/Psychic the ability to easily take on Clefable and Toxapex.