Yeah, I just went through that. I went back to Xenoblade to (finally) finish off the superbosses, and the Avalanche Abaasy (the last one) went on for half an hour. Now of course many RPGs out there have superboss fights that go on longer than that, but it's the way it went that rubbed me the wrong way.
I went in with a party of Shulk (player-controlled), Sharla and Seven. The plan was for Shulk to spam level 10 Monado Armor nonstop, while Seven spammed her OP auto-attack (not joking here, the only art I had equipped on her was Speed Shift) and Sharla healed and supported. Here's the problem, though: 805300 HP with 40% physical damage resist is a LOT, too much to take it all off in a single night (which lasts ten minutes) with that setup. And after ten minutes the sun rose, which negated Shulk's and Seven's Night Vision gems (as well as the -15% cooldown at night skill which I had equipped on everyone). That meant almost zero damage other than Sharla's Thunder Bullet (thanks to another skill link), so I had to deal with Sharla having the aggro ring all day on top of that. The only thing keeping me alive, aside from healing art abuse, was that skill Shulk has that refills his talent gauge when he has a vision, so I could at least use Monado Armor and the occasional Monado Shield then (remember, auto-attacks that miss don't fill the talent gauge!). And trust me, EVERY SINGLE ATTACK gave me a vision once the previous Monado Armor wore off. This went on for 14 minutes, with a very close call during sunset due to one attack that DIDN'T warrant a vision for some reason, and that I luckily survived due to an Unbeatable gem (I suspect the gem triggering was the reason why I didn't get a vision that time). By the time the second night began the thing was down to about a quarter of its HP, so it was relatively smooth sailing from there.
Still, 14 minutes of absolutely nothing happening is something you don't want your boss fights to have. I'm sure there are some teams that fare better (read: ether users), but if you're going physical you're probably going to have to deal with that regardless.