Dragon Age: Inquisition will have four-player cooperative play like Mass Effect 3. However, the player count seems to be the only similarity between the two games' multiplayer modes.
Inquisition's co-op isn't the wave-based survival mode we saw in ME3. Instead, it features randomized adventures designed to be played for about a half hour. Players will travel to one of three locations: Elven Ruins, Tevinter, or an Orlesian Palace. They'll then battle through hordes of enemies, including minibosses.
There will be twelve multiplayer characters, each based around one of the three base classes in Inquisition. Each character has a distinct appearance and set of abilities. Their skills can be upgraded as you gain experience. New equipment, recipes, and other items acquired through missions will also help them grow into formidable warriors.
Your various characters can be managed through an "Inquisition HQ" app for PC and mobile devices. The app enables you to change their loadout and craft items. Hopefully this means you'll spend less time micromanaging your characters within the game and more time actually playing.
The levels will be randomized to make them more replayable. Each map is made up of five areas randomly chosen from a pool of ten. This randomization isn't as extensive as what you'd see in, say, Diablo or Path of Exile. Still, it at least ensures that players will have incentive to tackle a given location more than once. They won't see everything during their first time through it.
Dragon Age: Inquisition's multiplayer is somewhat connected to the single-player. It takes place during the same time period during the campaign. The co-op characters are front-line soldiers single-player hero's mission to restore order in Thedas. There's not much storytelling in multiplayer, though. The focus is squarely on combat.
In Mass Effect 3, playing the co-op made it easier for you to get the best possible ending. That won't be the case in Inquisition.
"Our goal with Dragon Age multiplayer is not to affect your SP campaign," BioWare said in the official multiplayer FAQ. "We simply want to give our fans the chance to play with their friends for the first time in the Dragon Age universe."
Furthermore, you can't transfer items between single-player and multiplayer. The main edge you get from playing online is that you become more familiar with the character classes so you can more effectively use them in the campaign.
Inquisition's multiplayer will, like many EA-published titles, feature microtransactions. Players can buy a currency called Platinum to speed up their progression. However, everything that can be unlocked in co-op can be earned through gameplay.
BioWare plans to add levels, characters and other content to multiplayer after Inquisition's launch. This DLC will be included in free updates, thankfully. This will prevent the player base from being fragmented.
Dragon Age: Inquisition was recently delayed to November to give the team extra development time.