Soloing Crystal Cove (with or without a hireling) all depends on your build and how you play it. I have soloed CC lv 24 with my lv 24 Paladin, without hire, several times and averaged around 160 dragonshards as a reward. Granted, you sometimes get a map that makes it harder but, usually, it is very doable. Most of the time, you really don't have to stray far from the main chamber to get you 100 shard quota. I've found running east and down to the waterfall (after clearing the small south cavern) to work best. While they are clearing the south chamber, set torches down to the waterfall then place a teleporter near the first decent sized batch of crystals (purple or green), and gradually advance it to the waterfall.
If you find you can't solo, try posting for a group. You will almost always get at least one other player willing to join (although this may be more common at epic lvs). Good luck