The two main reasons to stay away from a closed-end fund - too expensive or a distribution (usually a fat one) that isn't sustainable, and the eight added to Wells Fargo's "closed-end funds to avoid list" fit the bill.
The eight: The GDL Fund (GDL), Cushing Royalty & Income Fund (SRF), Guggenheim Enhanced Strategy Fund (GGE), Guggenheim Enhanced Equity Income Fund (GPM), Guggenheim Strategic Opportunities Fund (GOF), Aberdeen Australia Equity Fund (IAF), Pimco Income Strategy Fund (PFL), Pimco Income Strategy Fund II (PFN).
Like many fixed income CEFs, the Pimco funds have seen earnings declines, but the Wells team notes it's been particularly significant for those two, resulting in distribution coverage rates of just 65% and 77%. Given the continued low rate environment, either the distribution will have to be cut or NAV will erode.
The Australia fund has an 11.8% distribution rate - hardly a fit with the 0.1% annualized NAV return over the past three years.