Very tough card to rate as it's extremely scenario/campaign dependent before you even consider how it fits into your deck. Obviously strong when you can actually play it, but how often does that happen? How often is the scenario result decided before this becomes playable?
Personally, I think this card is a bit of a trap in most cases. In a lot of scenarios, the toughest part of the game comes early, and the result usually comes from which way the game started snowballing. Either you easily handle what the encounter deck throws at you, get your engine running, and cruise to victory, or you suffer some setbacks, waste resources, and get stuck until your doom is assured. This card isn't needed to win in the first case, and does little to prevent the latter.