how do ya know? itll show the red damage numbers but thats not really hitting. did you have a red/noncontrollable summoned and hitting andros with nothing else hitting him and it moved his hp bar?
if the boss is full hp, and you spawn an Energy vortex near him, his bar will go down. plus you could speed the whole fight up by having someone spam summoning spells (BS,EV or the one thats obviously the best as it doesn't get auto-dispelled, and saying this will more likely nerf it.. but, Natures Fury) do between 4-12 damage Per hit each to Andros. (After Discord)
When you sommon an EV or BS they have about a second or so to hit the target before they get dispelled, the message that pops up states - any tamed/summoned pet that requires more than 1 control slot is auto-dispelled or removed from the encounter (natures fury takes 1 slot per summon, thus you're able to use them in the fight.) they speed up the fight quite noticably as opposed to Not using them.
you could theoretically kill the boss solo if you're able to keep your possessed pet alive for the whole fight... (vet-pet / mana for nature's fury spam) ?