Yes, it is important that Europe have its own defense independent from NATO, because NATO might have different interests than Europe by itself might have. It is important that Europe maintain its own defense force, without being beholden to NATO, because the two might not always agree on the best course of action. Every nation should maintain an independent defense force, just in case the political climate warrants using it.
There is truly no reason that the world needs another powerful sub-bloc of countries whose soul goal is to protect their own interests. There are very few (any major?) matters of foreign policy that fall out of the interests and scope of NATO/the UN, but that need to be tackeled by more than one or a few European countries.