I re-point out that Orb of X description have two separate paragraphs, that to me denotes some measure of separation between the effects of a spell. that section is called "Descriptive text", not "effect", but much as I like arguing semantic, I understand where you're coming from here, I colloquially call that the spell effect, too.
I can do bolded quote too, specifically that the actual text of orb of X are "... fortitude save negates ...", and ray of exhaustion is the perfect use case of it indeed being completely negated by mettle as opposed to partially negated (no argument here, we agree), I don't know how to do that without sounding confrontational, so if I'm sounding confrontational, I am giving out reassurance that I am not being confrontational.
for a moment I misread that as "lesser orb of fire" and I was confused, but this brought this thought to me : I find there to be some argumentative wiggle room that "Orb of X, lesser" have no saving throw, therefore the damage portion of "Orb of X, lesser" is behaviorally the same, and the fortitude save clearly ( to me ) refers only to the sickened/dazed/etc, and negates that.
agree to disagree, I suppose?
Are you talking about Hexblade Mettle or Pious Templar Mettle? I'm more likely to accept Pious templar Mettle to completely negate a spell, because that's what it says it does. Hexblade Mettle does not say "completely negate the spell", it says "completely negates the effect"(implied, to me : "..the effect that would otherwise (do something) on a successfull save.") ( and the implication of the implied is that the damage of Orbs have no relation to the secondary effect of causing some debuff with fort negate )