Yeah, that was the most frustrating of all the story bosses I faced. You are doing the right thing, but I think to win once that particular target reaches half way or below, you HAVE to hit it with chain attacks. I tried having the AI allies target while I distract the other portion but that never worked, focusing exclusively on the target just leaves you exposed as once it reaches a certain point the attacks ratchet up. Chain attacks are your best offensive and defensive (ie when it goes for a big attack chain attack right before it lands even if you don't have the orbs necessary for major damage) path to victory in most of these frustration battles story and super bosses.

Hey, maybe in the expansion.

That would very much appreciated.

I did use the right blades, as how can you not, the suggested field skills aside from unique exclusives and expeditionist are element masterys. However, shaving of a mere 1-5 min hardly helps unless you're just sitting there staring at the merc screen, since otherwise you're doing something and wont always check in the second she's done. Even if you do just sit there, 10-15 hours is still outrageous and inexcusable.

Oh, and after she gets Lv.5 affinity, she needs 7k trust to actually complete the chart... just lol.

Are chain attacks essential? Cos I hate using them as it totally depletes my party gauge and leaves me vulnerable to being cheesed without any points left for revival.

Hm..well you might be farther than me now (I've been waffling with the game since I've been on vacation and didn't want to do serious story stuff with the handheld), but I've yet to get in any fights that were unwinnable without using chain attacks. 

It's all about risk/reward basically...I try not to use them unless I'm confident it'll do enough damage to warrant leaving myself open. It's like an all or nothing suicide attack. Obvious tips, but I wouldn't even bother using it unless you're able to use at least one elemental burst, and make sure you have a healing move ready to use when it finishes, just in case.

In the last few chapters most bosses start hitting pretty hard after you get their health down. The easiest way to beat them is to get elemental orbs on them through combos and chain attacking once their health is down to the point where they go berserk. You should be able to overkill the boss at that point. 

It is possible to kill them without doing this, but you bettwr focus on have a buffed up healer and reliable tank. It will take longer too. 

Chain attacks are as much a defensive measure as they are an offensive one, but you have to use them properly. It takes a while to get a hang of it, but once you do it makes battles almost too easy.

They just don't feel like a worthwhile payoff to me; I'd rather just prolong the battle another few minutes than run the risk of getting one hit OK'd by some bullshit attack the enemy pulls out of its arse at the last minute and having no revives. Losing your whole party gauge just feels like far to steep a price. It should deplete one segment, like a revive, I reckon.

Well yeah, you shouldn't often be doing a chain attack unless it is going to kill the boss or you filled your party gauge pretty early and expect to get another full gauge later to finish the boss off. Chain attacks would be too overpowered if it only depleted one segment. They are already pretty overpowered, especially after a certain story event which makes them pretty easy to do effectively. 

Personally I rarely allowed my party members to die, because this often lead to aggro being transferred from my tank to the more squishy members of the party, which usually meant losing the party anyway (you can only revive so many times.) 

It's all about timing and planning.  Like sc said, it only depleting 1 segment would make chain attacks ridiculouslu OP.  The way I approach it is to execute a series of blade combos to accumulate 4 or 5 orbs and then chain attack when ready, when the boss was under half health usually.  A combo that breaks 4 or 5 orbs will kill many bosses once under half health.  Also, I think 5 orbs is the point where you can max out the chain attack gauge which let's you launch a big attack on top of everything else.  

Okay. So help me out for a sec; when doing chain attacks, does doing just one move break an orb, like a water attack breaking a fire orb? Or do I have to build up combos of 3 attacks in a row like in regular battle?