wait until taken king is installed before you shard any legendaries. Those armor pieces decide what your starting level will be and if you delete them your character will be level 20 instead of level 34 on release. also those legendaries are going to be the weapons and armor you use when you first start playing TTK, you actually have to play to earn the better new stuff and you need things to play with in the beginning. also there will be enough vault space to keep your old gear if you really want. also it will still be useful in crucible and older content.