Holy Water, I've used. Specifically that fight in the Highlands where there's the 2 dudes with the aura that reduces all non-Radiant damage they take which have a full resurrect as a bonus action. Was it any good? Not really. But considering anything besides Spirit Guardians there is kind of awful it's at least something.
Arsonists Oil/Oil of Diminuation/Wizardbane Oil I just never use. Heck Oils in general I just don't use. I'd rather just dip my weapons in a Toxin which lasts until Long Rest than waste even a bonus action during a fight.
Remedial Potion I've used on a couple of occasions. There are a handful of enemies that cast Blind which can be annoying. Throwing it on allies who are Paralyzed could be an option, but I never remember to do that.
In the end, some consumables simply come down to frequency that they're useful, Remedial Potions and Arsonists Oil would be more memorable if situations where they were useful happened more often (Also, with the amount of Basaliks Oils you get in Act 1, I imagined Petrify would be a more common issue than it is).
Other consumables simply fall by the wayside because of other options competing with them (Holy Water vs attacking? Wizardbane Oil vs just using Long Rest Toxins?)
Of course, there are ways to enhance the usability of some consumables. Like Holy Water you can drop on the ground and have a Mage Hand toss them at undead/demons for free action economy (Same tactic can be used with regular Water to apply Wet status for free and enable double Lightning/Cold damage for your mages)
