You destroy cory's army at haven and you destroy his back up plan when you save the wardens.
cory's army isn't complete destroyed after haven but indeed he lost many of his warriors.
what we should think about is the fact that the rest of his army is spread all over orlais and thedas.everywhere are little troops of them.
parts of his army seek artefacts in the hissing waste ..the forbidden oasis and the western approach...other parts fighting against
the royal army of orlais in the exaltet plains and emprise de lion also against the rebels of the emerald graves...and so on.the most of this battles are only skirmish.
orlais is huge and cory didn't concentrate his army on one spot of the map to make one big battle after another.
after haven he use the rest of his army not really to make one big war ...maybe they are not able and not enough warriors to do so.......they are more seeker and searcher to find something powerful to make cory stronger.other ones of corys creatures are only up to terrorise the citizien of orlais but not able to make a big battle.but to be fair we shouldn't forget some war table missions where parts of cory's army attack villages and nobles and so on.
the only big battle after haven is the adamant battle.
but who is in his army ? his army is a mix of different creatures and warriors:
the demons and ghosts , the red templar, the undead,the warden , the darkspawn,calpernia and the venatori.
cory loose with every skirmish more and more warriors everywhere in orlais.he will be weaker day by day and his man can't find new artifacts to keep him strong or to make him stronger... and if they find something...the inquisitor will be there to prevent that cory get it.the alliance to defeat cory is too big.whole thedas is fighting against him.
into the arbor wilderness fight a reunited troop of the last warden...venatori and red templar against the strong inquisition.