Well, Twintania back in the day seemed to have endless HP. But with Echo at 20% and ilvl130 gear and 135 weapons, people can reap her a new one in record times.
That aside, Coils of Bahamut is a sidestory, not part of the Main Storyline, so its not obligatory. If you're familiar with Final Fantasy, you should know that most of the games had what's called superbosses, which are optional content. The Coils and Extreme Primals are just that.
Oh, and if you think Twintania has HP, just wait until you make it to turn 13