Wither behavior only changed for uncontrolled, unsummoned monsters. The behavior when cast by players should still be the same.Wither friendly fire = in coon(example) can hit anyone not in party, bug?
To clarify how wither picks (or should pick) the targets when cast by players; wither will not hit guild, allied guilds or party members ever (including their pets), any remaining mobiles are hit when either you are red, or when they are not innocent to you. Facet rules are applied on top of that, but in your example, located in Felucca, that doesn't change much.
If what you experienced doesn't match the above, there might be a bug. Let us know if so.