These healthcare giants can survive the toughest challenges.Dividend stocks aren't all created equal. Some decrease their payouts, or suspend them altogether, when they face headwinds. Others have much stronger businesses and continue to raise their dividends even as they face obstacles. Income seekers want to stay away from the former and invest in the latter. One imperfect way to determine which is which is to look at their track records.Of course, the past doesn't guarantee anything, but companies with a ...