Disaster Declaration Improvement Act - Directs the Administrator of the Federal Emergency Management Agency (FEMA) to issue a revised rule governing factors to consider in evaluating a governor's request for a major disaster declaration to require: (1) the "estimated cost of assistance" to be considered equally with the other five factors described in the rule; and (2) the "evaluation of localized impacts" to include consideration of the budgetary resources available to local and state governments to respond to and recover from such disaster and the impact of the disaster on a small city or a census-designated place with a population of less than 25,000 or a medium city with a population of less than 250,000 if either is located within a large county with a population of more than 1 million and in a large state with a population of more than 5 million if the level of financial damage in such city exceeds 10% of the city's general fund or $100 per capita of the census-designated place or city.