The objectives in Outbreak aren't particularly out of the ordinary, usually boiling down to defending a room while zombies rush you.
Zombies appear to spawn randomly, meaning that you can run into a Smasher (Outbreak's Tank analog) during one encounter while at other times the Smasher may be replaced by an Apex, what is effectively a magical zombie that spawns other zombies. You and two other people have to make your way through a map that is infested with zombies while completing a few objectives along the way. While Outbreak may be a rather unexpected change of pace for Rainbow Six Siege, at the end of the day the only thing that matters is the one question that permeates all of gaming: is it fun? Conceptually, it's not redefining the wheel, especially if you've played Left 4 Dead before.
Thanks to the Operation Chimera update and the associated Outbreak event, you too can shoot fast zombies, big zombies, exploding zombies, and magical zombies in a game that you would've likely never expected zombies to show up in at all. Yet, almost half a decade later, there are now space-based parasitic zombies in a game that prides itself on being reasonably realistic. When Rainbow Six Siege was first shown off at E3 2014, it seemed like another run of the mill modern day military shooter from Ubisoft, at least from a thematic standpoint.
