It would've been better, I think, if the whole of Vegnagun was one continuous fight - from the tail right up to the head. The problem is that you're free to go away, save and heal after defeating each section. If you had to do it all in one go (like the Tiers in FFVI), then the pressure would be greater.

However, if you're looking for some real challenges in FFX-2, try the Via Infinito in St Bevelle. Some of the toughest opponents in FF history await