So I've noticed
Fire Giant Warriors in SolB are currently incapable of receiving any beneficial spells at all. When they are KoS everything detrimental lands on them as long as you are under the mob.
However, once they are charmed player cast spells are nearly incapable of landing on them. I tried repeatedly to buff a charmed fire giant with every kind of buff I could imagine only to have all but 1 spell resisted. I got a haste buff to land once but resisted about a dozen other times. Heals were incapable of landing as well once charmed basically making these belly caster pets 1 and done cannon fodder.
I did note that even though no player spells seem to land on them any spells cast by other mobs still land without issue on these charmed belly casters.
Charmed some other stuff and buffed to test if it was a server wide pet issue or something specific to the zone but the FGs were the only things effected. Note that I have not tested with other belly caster pets in other zones so it may be specific to these mobs and only these mobs.
I didn't get any screenshots or fraps of these issues but would be happy to go back and get some more solid evidence.