They indeed are rare. Singlemod are significantly more common than gold spikeds (l get 2-3 gold spikeds a year and l get 1 gold str wooden a week on avg - but all single mod!) . Dual mod might be same alley as gold spikeds. Also gotten only grapes from mantids btw, quite possible they can't drop them gold
I'm not as pedantic with numbers as Agent Chevy is so have no idea how many runs l make, which is a good thing as it makes possible to evade some introspection on use of my time lol
Jonast problem is yetis, beyond SV, have kd and are powerful healers, so most builds don't work on em. And l'm not ready to pop a consent to kill up to 30 yetis (before the tengu do to make it worse!) with some funky sc-esque build to test the spiked club more often from them theory. Also l've killed plenty loner yetis and they haven't produced spikeds in any rarity l'm fairly confident.
