Quote: TacoMakerSkysThing is I played DDD. A lot. I played through it 7 times on 3DS, but I ended up buying it just to experience 0.2 and DDD in HD. I love 0.2 but God damn the final boss is no joke.
Main thing that helps with it is that you can skip the second phase if you stall on using Wayfinder. When Mickey starts riding the swarm, the Wayfinder Situation Command appears for 30 seconds. Instead of using it as soon as it shows up, keep piling on damage while Mickey rides around on it, as it will not attack you at all during this time. Then, when the Situation Command is close to disappearing, use it to lock the swarm in the chains. Then, instead of mashing Attack like the game expects you to, use up your Shotlock on the swarm while it's bound by the chains for massive damage. If you want to use another gauge of it, use an Elixer. You can also pile on Magic attacks for Magic finishers. Another way is to mash Attack as normal, but when the Finish Situation Command pops up, don't use it. Keep mashing and I think you can keep resetting the Command if the animations time correctly.
You can't actually finish the boss off during the first phase, but you can get it down to 1HP this way. Then the second phase starts as normal, but since it's at 1HP, you just have to hit it once and it's done.
Here's a more complete and thorough guide for the whole fight if you need it.
Also, make sure you've downloaded the 1.02 patch, since that flat out makes the combat a lot smoother. This boss in particular also got a health nerf on the patch.