Well, unfortunately, that's what happens in random groups. Optional Content is where challenge should be, because that's done by groups of players who know each other, who choose to do said optional content. MSQ fights should not be that hard for that reason, because everybody is pretty much forced to do it.
And again, the boss is out of balance. The last fight in Heavensward is The Griffin, which is far easier. He telegraphs his attacks in a way that makes it very easy to understand what he's doing. Or, if you want to talk about 8 person fights, Nidhogg's Shade is even easier. He has some attacks (especially that stack mechanic) that can kill people, but again...
1). No Permadeath, which means peeps can be rezzed.
2). He, too, telegraphs what he's doing and the mechanics can be understood without the need of a wiki/guide/what not.
Ravana is just out of balance, there's no way to refute that.
