Also happening with my friend and I. Only Legendary Wurms count (Triple Trouble etc). If it get's fixed soon, would recommend going into Twilight Arbour Dungeon (Explorable) and farm the section which is 1 min or so in with the Wurms as they're all champs.
**EDIT**
Don't bother doing PoF Leggy Bounty Wurms, just tried it and it does not work. Only one I know that works in the Great Wurm in Caledon Forest.