Raviente's fight is entirely different because it's a server-wide multi-stage fight. Amadyura tries to take that idea and convert it for vanilla small scale MH, but honestly it just feels like a split Jhen with some Dire Miralis in the mix. Raviente is way more dynamic while the Amadyura spends the majority of his time sitting still for you to hit him.
Deviljho is boring to fight. Savage Deviljho at least looks cool, but once you learn how to dodge he's just a matter of constantly hanging out under him poking his belly.