From what memory serves me, every battle before In For Garuda Wakening is pretty easy for an average group of level 50s, most can also be doen at level 45 but it's harder.
You'll need to fight some NMs, not that hard, get halfway through one or two dungeons, I think only in Dzemael you'll need to get past the mini-boss. That's doable even with a smaller party (actually don't remember if Dzemael is part or not, but Toto-Rak should be vastly easy to accomplish with two 50s)
And then there is In For Garuda Wakening, if you're careless you WILL wipe, but it's no end of the world. Then there is United We Stand, that is also difficult since not only it requires going through Castrum Novum but also takes a bit of skill and attention as the fight is quite unusual and the nthere is To Kill a Raven that is, from what I hear, pretty hard.
That said: Also there will be at least one or two NMs to be killed for promotions.