Can I get some more information on this issue? I'm fighting kree'arra atm and my range protect is reducing the damage perfectly fine.
According to reports, and personal tests, protection prayers seem to be less effective than before the most recent update.
When the PvP update came out, there was an issue where protection prayers were overly buffed against NPCs - GwD bosses could hardly do any damage at all - so Arc fixed it. It seems, though, that the prayers may be too weak now.