You could actually merge the two though it would require manipulating both's lore a bit. For starters you would have to replace the fact in Dragon Age dragon's are mere beasts excluding the Archdemons but the Archdemons themselves are not dragon's but the Old Gods who were said to of taken on the form of Dragon's. So instead you might have to say I don't know the Archdemon's were basically the Lords of all Dragons before the Lords of Men, Elves, and Dwarves fought them. 

Once that was done great kingdoms rose but a curse spread called the Dark Sign but those cursed with it were given new purpose, to fight off demon's (rather then darkspawn) that came to being after some events. The Archdemon's then have come forth and you must defeat all seven.

I really put to much thought into that. XD

But yeah it's possibly just like I said before, it's a manipulation of lore.