To address your (a) comment, some countries have implemented close approximations to NGDP level targeting after the 2008 crisis, and have done well. They include most obviously Iceland (despite a severe financial crisis), and some less obvious instances like Australia, Poland and Isreal. One could point to the UK as the clearest counterexample, but just about everyone agrees that they have severe structural problems, which NGDPLT is not intended to address. And even then, monetary easing has allowed the conservative government to implement fiscal austerity without crashing the economy - this was widely expected to happen and there was a lot of public concern (compare the situation in the US wrt the "fiscal cliff" and "sequestration" scares. Here too, the Fed offset the negative fiscal effect by printing money).

As for (b), nobody argues that money hoarding is a bad thing per se. But it needs to be offset, because practically all prices in the economy are expressed in terms of money, and the price system cannot take the impact without severe side effects and misallocations. Inflation targeting is a very rough way of doing this, but it's just not good enough (see George Selgin's book Less than Zero for an argument to this effect). ISTM that this is not well understood in the mainstream ("NK") macro literature, where supply shocks are confusingly modeled as "markup shocks". I have seen cutting-edge papers pointing out that these make inflation targeting unsound (sorry for not having a ref here).