Drat is a shortened form of 'God rot', which is an oath of long tradition. Normal usage would be of the form, "Drat these editors!", meaning "God rot these editors (in Hell)!" This expression is seldom heard nowadays, except by people who wish to make an imprecation without sounding vulgar or profane. Compare this usage with 'God damn these editors!" or "Fuck these editors!" It is also used to express annoyance, as in "Drat!" or "Drat, drat, drat!", which compare with "Damn!", "Shit!" or "Fuck!"
Drat is actually a profane term for Christians, as it indeed represents an irreverent use of the name of God, and it is certainly a curse, even though modern users may be unaware of its original sense.