The mission itself is one set of waves of enemies, with the grueling gauntlet having to be restarted again if you die anywhere along the way. It loses any sense of progression but enhances the feeling of repetition.
According to Yodamanjaro:
There’s a reason why my friends and I, who’ve got all 150+ hours in this game, haven’t even bothered with Incursions. That reason is that it’s not a real mission, it’s just horde mode. No point to playing the game at this point.
Others have stated that the Incursion is more of a Horde Mode than a raid. But even then, it’s not as fleshed out of a Horde Mode than it could be. The reddit thread praised Mass Effect 3, Borderlands, and Halo Reach has example of doing multiplayer right.
Ratch_V had this to say:
Incursion just isn’t any fun. You have waves of npcs, then drones, then npcs. The APC sits in the same spot and just shoots a missle at timed intervals. It never changes tactics. You do the same thing over and over for 15 waves, killing npcs, pick up bombs, turn off turrets, put bomb on. The turrets are permanent and can’t be turned off, and ther is no progression during the fight. You are more or less limited to a couple of spots in the room as being practical to use.
The biggest imbalance caused by the Incursion events are rogue player teams that demolish casual players en masse, making it a highly unfair playing field for people who don’t have all day to play the game.