Thx for the reply, eventually I tried something different.
I teleported back to Arx, tried fixing a bit my equipment, potions, runes, skills etc., then went back to fight. Well, this time the Kraken summoned the adds right where they were supposed to be summoned, next to Braccus. Everything went down smoothly, so finally I can say it's over.
Maybe Larian was just trying to test my patience, who knows... :)
