I do feel curl's pain though. It sucks when you're just minding your own business, taking out some monsters, and some OP one shows up out of nowhere and just destroys you. It's really annoying. It's also bothersome how some enemies nearing death suddenly do attacks that just murder your party, and that fight took some time to dwindle the enemy's health that low.

The reinforcements can be avoided by putting a dark orb on him.  Water > Water > Dark is a quick easy way to put that up.

I swear I am this close to flushing this game down the toilet.

Jin in chapter 9 is bullshit. Any time he feels like it he can just spam his shitty overpowered arts and kill me, and I am 3 levels above him. There is nothing I can do. On a whim he can just hit my party for half its health, ban all healing, one hit my tank, all in the space of about 20 seconds.

Use Mythra and equip a diamond accessory, a modern medal (or avant garde if you have it) and give her aux cores for Crit Chance V and Arts Heal V.  This with Rex will give you constant healing.  Also use Narcipear Jelly and the Plumber Game for pouch items.

Seal his abilities quick, get to 3 (and if you can hold out for it 4) orbs and then pop the chain attack with your most powerful team and blades.

I did this and the game basically became easy mode for me.

Healing is almost useless though; his evasion is so stupidly high that most of my arts that drop potions miss, while he keeps nulling healing. I have gotten 4 orbs (fire, water, wind, light) on the guy but it doesn't seem to stop him using any of his stupid overpowered gimmick arts.

I do feel some of curl's pain here, game got really annoying at times for me as well, most sessions for me were incredibly mixed. I even had to take a 2 weeks break from it.

Main problem probably was since I wasn't super invested in everything from the game, I'll keep running into hurdles, to an extent what happened with me in the original Xenoblade tho not as bad.

The moment you have 4 orbs use a chain attack.  If you break all 4 in 2 rounds you get full burst and that should drop at least half his health if not more.  Keeping him from enrage and getting him down quick.  Its unfortunately the formula for every boss from that point forward as well as the post game monsters.

I swear we aren't playing the same game.  At that level you should be steamrolling this guy.  I encountered hardly any of these issues :/. 

Phew, after 5 hours of grinding robots and tinkering with my party and 6 attempts, I finally got the bastard. I don't even feel like I improved or achieved anything, I just feel like I got lucky. Usually he strings together 2 or 3 of his arts in such close succession it just slaughters me, but this time that just didn't happen.

My main issue was that I couldn't get a full party gauge on him cos I kept having to revive my team mates, but this time I somehow managed.

I didn’t really do anything special to get through stuff. I didn’t have any difficulty after chapter 7 at any part in the story. But I did do the following:

1. Kept merc teams out on missions.

2. Kept spending extra XP at Inns.

3. Used Rex, Nia, and Morag.

4. I kept all the Affinity stuff up to date.

5. All the dozens of items that needed equipping equipped. My tanks used high block items, and everyone else used stronger attack items.

6. Always had stuff in my pouches, but without any real thought put into it.

7. I got all of the Arts maxing skills for all characters, the ones that have Arts ready to use at the beginning of battle.

Doing combos did lots of damage to groups of enemies. I was usually able to snap them out very quickly. I rarely used anyone but Mythra, And found her level 2 special really bumped up the party gauge. I used the twitch attack a lot because it bumped up arts quickly.

I also killed almost everything I came across toward the end, aside from some mini-bosses, I ran from those... except for one who was guarding treasure.