I think this is good case of Black Swan (it would be highly improbable the same problem hit all the companies in a diversified portfolio but could happen a la hearthbleed).
There's an extremely insightful book written on the subject (the black swan by Mr Taleb). Wich I do recommend.
Discounted cashflow = bullshit used to rationalize the sale price ( it can have some use in super long term predictable business like real estate with 10 year lease and well diversified tenants)
Discounted cashflow = bullshit used to rationalize the sale price ( it can have some use in super long term predictable business like real estate with 10 year lease and well diversified tenants)
Hope this was helpfull