Between the greyfeathers and the divine sets which would be better?
The greyfeathers has normal defence and no shadow and the divine has no normal, but shadow.
The divine seems better, right?
Also, what sword would be the best paired with a leviathan. I'm thinking one of the fast blades?
If you use divine, you need to make sure to still use another piece of armor with it that has plenty of normal protection since tier 3 still has lots of sources of normal damage.
As for swords, if you are going to be a swordie you want to avoid normal damage swords and use elemental, shadow, or pierce swords for getting the most damage versus monsters. Anyway, even if you do make the calibur line, it's probably not necessary to go beyond the 4* ascended calibur since leviathan is not really any better. A DA or GF would be better paired with a fast sword.
You missed that third, perfectly good 5* Magic line known as Chaos.
LOL Perfectly glass cannon. I think the OP sounds new enough that he or she should probably wait on getting armor that is so unforgiving of mistakes.
(No offense to the OP, just it takes time to get skilled enough. I know I wouldn't do well in it considering how much I get hit still.)
Leviathan is a fine sword for a swordie. Great for Vana's mask phase, so if you don't have to much difficulty on the levels before and like to do Vana a lot, the Leviathan is good. Also, its charge can be used for different situations. It can knockback everything around you, or, if used right, can pound massive damage in the backs of your enemies.
EDIT : Sorry, didn't give my opinion about what 5* magic cloak xD
Go with Chaos :3
divine veil and valkyrie mail should smoke all those fiends, you can also use it in FSC since there's no fire weakness.
Divine Veil is better than Divine Mantle, due to the bonus fiend+2. And you don't want to wear both Divine pieces at once. So Divine Mantle does not fit into any perfectly optimized armor set. Sorry. How far into that alchemy path are you? Even if you're already at 4-star, it's not too late to switch. More than half of the cost of making a 5-star item comes in the final upgrade from 4-star to 5-star.
No sword pairs perfectly with Leviathan, because Leviathan is a sword for people who use only one sword. As soon as you're using more than one sword, you want them to be of distinct non-normal damage types. For much more detail, see my sword guide.
Edit: Sorry to be such a downer. The truth is that Grey Feather Mantle paired with some normal+piercing or norma+shadow armor would be fine. Divine Mantle paired with some normal+piercing helmet would be fine. You can play the game with these sets. They're just not the best.