Yeah the Henne Mines make me sweat
Also, I just had a crazy experience in The Great Crystal. I wanted to get Excalibur so I tried to make a B-Line straight to it. I was reading off of two maps, ones layout was better to understand but the other had the correct treasure placement for the International version. So I finally reach the screen with Excalibur and come to find out the Ultima fight is NOT optional here (which, for some reason, it states in the International Map version). So I'm like "fuuuuuuck, I really want Excalibur" and decide to half ass this fight and see if I have a chance. Long story short, my Level 17 Balthier (everyone else is averaging around lv50, Penelo at 70) saved the day with Gil Toss. I had saved up around 200,000 Gil and set Balthier to spam Gil Toss at around 9999 to 10,000 damage per toss. I also mixed in some Mist attacks when my Techniques were sealed and couldn't use Gil Toss.
But even then Ultima goes all crazy with her big attack at the end. Just as I was about to be wiped with my final characters in play, I use Vann's Mist attack as a last ditch effort to finish off Ultima. I needed a 5 Combo at least with either Basch or Frann with Vann and got it.
That experience alone has placed this game very high in my opinion of it among other Final Fantasies. I don't remember having this intense a battle in a FF game and actually come out victorious.