I note that the two unions you bring up are public-sector unions. It's worth considering that public-sector and private-sector unions are different beasts. For one thing, private-sector unions are facing off against corporations - both trying to maximize their own value, and so one might hope a balance is achieved. In the public-sector, unions are trying to maximize their own value, but the government is (hypothetically) trying to maximize public good, so it's not really a fair balance.

Private-sector unions have been hugely helpful in the US. This article touches on it in an interesting way: http://www.nytimes.com/2015/02/19/opinion/nicholas-kristof-t...