5. It's Not Really Newcomer-Friendly
I get the sense that a lot of people will be coming to Inquisition without having played the first two Dragon Age games. Those people are going to have to do some background reading, because for better or for worse, Inquisition is hugely reliant on the lore, characters, world-building, and backstory laid down by the first two games. If you don't know a Tevinter Magister from an Orlesian noble, you're going to be a bit lost here.
Dragon Age: Inquisition also places a surprising (welcome!) focus on politics, specifically the civil war raging in Orlais, the nation next door to Origins' nation of Ferelden. If you're a bigDragon Age nerd like me, you're probably super psyched to hear that, but it does mean that newbies will have to spend a lot of time actually reading the game's (enjoyable and well-written) codex or tracking down some entries on the Dragon Age wiki just to keep their head above water.
Furthermore, several of the plot's twists and turns rely on knowledge of some pretty specific events from past games. Even seasoned players will want to brush up on Elven mysticism, the Tevinter Imperium, the legend of the prophet Andraste, the hierarchy and schisms in the Chantry, and even the events of Dragon Age 2 DLC just to understand why a given plot development has everyone worked up.