since OOW has come out , i have made 3 pairs of these , 2 i sold for 250k each and one i kept . As Saraban says , the Pyrilen Flames (drop in riftseekers a 69+ zone) are damn rare , although early in OOW release I was lucky enough to see 2 on a NPC vendor for 12pp each hehe .
They are triv at 288 iirc (will check tonight) and I havent failed one combine . (my skill is 252 + 5% mod , not that it matters )
Well, they are trivial way beyond 250, so they *are* quite difficult to make, but the real bottleneck is that you need 4 Pyrilen Flames per combine and those are really, really rare. Expect less than 1 per evening of exping in RSS...