Fiend-Blood Bat's are geeting a SR save against Ottos...Ottos description says..Spell Resistance:No
(Combat): You roll to see if your spell penetrates Fiend-Blood Bat's spell resistance. You roll a 10 (+15): spell resistance success!
(Combat): You hit Fiend-Blood Bat with Otto's Sphere of Dancing.
Not sure if any other mobs are getting this.. this is the only place i have noticed the blue flashes (making me check the log)...and since I have a battle bard I dont use Ottos many other places.