It's not that Atheon himself is more difficult, it's that certain people in our party are equipped and more experienced with going into the portals and taking out oracles and communicate better communicate with their designated team while on my end, our team of 3 are better at holding of the Pretorians and keeping the portals open while both surviving and dealing massive amounts of damage to atheon before they come out of the portal. We completed the raid after the patch, but there is no more team work and just confusion until the stars alight and the right people are sent through repeatedly..