The issue is that many readers still find a need to scapegoat either Lews or Latra. It seems to me that both had roles which had a part to play in humanity's survival, and neither plan had the capacity for complete success. In the grand scheme of things, their inability to work together was the Pattern's way of balancing itself to ensure that neither gained the ability to completely dominate the effort against the Dark One. The short term failure of one side lead directly to the short term victory of the other.