This is why Dragon Age uses fixed loot/drops. This way you don't miss a thing provided you have fully explored the map.
It is a huge work but I think Larian needs to make efforts to re-allocate loots.
Not everyone thinks Dragon Age was a good RPG. /shrug
My point is that this game has limited enemies/loot sources while applying a random loot system. So it is very possible after you have looted every single item there is still something offered by the game that you dearly want but you simply aren't lucky enough to have it.
You may not go for another playthrough just to get certain items and there is no guarantee that you will get them.
