I haven't read ANYTHING about what this Berserk does.
Base it off Berserk itself? And then add the animation tags "Morph" or "Alternate", maybe to the buff itself. You could try removing all spells that involve spell immunity when he finishes casting Avatar.
Finally finding about some of the bots that are flooding the users online - bytespider apparently is a huge offender here - ignores robots.txt and comes in from a ton of different IPs
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.