No. I was clarifying my interpretation of the rule, the bit where I quoted the rule is in quote marks.
Anggul and Zeshin, you have a strong point here.
I was initially thinking along the lines of "Immune to the effects of ID means that the effect (in this case no FNP roll) is ignored"."Instant Death doesn't ignore FNP in it's effect, it's FNP which disallows itself against Instant Death causing wounds."
That was my gut reaction to the rule, but as you pointed out "No Feel no Pain roll" bit is not an effect of Instant death or Eternal Warrior but an effect of Feel No Pain. It may still need a bit of clarifying in FAQ, but as it stands my initial view point has been proven incorrect.
Creatures with eternal warrior and feel not pain are quite tough enough already so I am quite happy that they wont get an "extra" save when you finally do hurt them!