It's not so much that it's difficult, it's just there's too many rules in place. You can't kill Typhon on turn 6 or you'll get wiped. But you have to kill it before turn 10. At the start they get a free kill on you. If you hit them with various elements it triggers certain attacks. If you don't hit them with other certain elements it triggers attacks. It just seems overly complicated. I like difficult fights personally, but this just isn't fun on paper.
For what it's worth, I found the fight to not be so complicated in practice.
But I ran Cecil, Y'shtola, Minfilia, Orlandeau, Friendlandeau. The only break you need here is ATK break, and I don't think it's optional, so even people who, say, have Aileen but not Orlandeau may want to bring him as a friend? I'm not sure.
Basically look at it like a checklist:
- Keep ATK break on Orthros
- Keep DEF buff on your entire party
- Make sure you count turns correctly
- Kill Typhon ASAP
- Burn Orthros while paying attention to thresholds; make sure you have Earth resist/SPR buff up for those
You can go either way on the Refia vs. Y'shtola thing here. I brought Y'shtola for the damage mitigation LB and Aerora access, which meant I didn't need to worry about bringing a wind elemental weapon for Typhon's sneezes. Hell, you could probably bring both of them and drop Minfilia entirely if you bring Barstonra? I'm not sure. Magnitude 8 didn't do that much damage.
It's mostly about making sure you don't push Orthros past two thresholds in one turn or do something else stupid like kill Typhon on turn 6 (which the wiki warns against like three times), which I did and barely managed to recover from.
Also don't forget to dispel Orthros after the 50% self-buff threshold. Not that I did that too, or anything...
Orlandeau remains the biggest crutch in this game. I guess that ends with Aigaion, but damn, what a run.