The highest I have seen that you can actually use is shadow leather equipment at level 74. For weapons the highest bow you can use is the GraveRobbers at level 74 as well I think. But what really makes an item shine at that level isn't the level of the equipment or its armor value, but the quality and nature of the mods on it.
And if you don't know how to get equipment that high, there is a third playthrough option beyond Hero and Legend. Its not advertised anywhere but you can access it by choosing "play now" with your lvl 75 character. You'll either start at the very beginning again by yourself or else you'll be randomly placed with other lvl 75 characters. The monsters are at a higher level and they drop stuff higher than what you can find fighting the Legend Dark Fairy, all the way up to the high 90's. You however, remain capped at level 75. I think you have to be online in order to access this third playthrough.