I don't know, Madman, maybe it's WC3 et seq. that's wrong because "Armada" says it takes a year-and-a-half. How should we judge a conflict between or among the games? A pretty question.
However, I certainly agree with you that there's a more important and overarching issue at stake. The pre-War history does suggest that Terran/Kilrathi space is difficult and time-consuming to explore, while some of the games portray it as easy and oh-so-quick to traverse. From without (the fiction writer's province), the conflict is easy to explain--to concoct a concise general history, one must extend years into decades into centuries using a limited number of story lines; but to give a detailed account of the turning-points of that history, in particular the decisive battles of a war involving specific places and people spread over interstellar space, the shorter the time it takes to travel from Points A to B, the more exciting the drama and action.
Our problem, though, is to explain the conflict from within. For myself, I've wondered whether a computer simulation based on the "background facts" implied solely by the games would, among the possible scenarios, successfully spit out a thirty-five year war. I have my doubts, in part due to the liberal "accessibility" the games require for the applicable regions of space.
Still, I'm not to the point where I think we have no choice but to make a choice between a cumbersome vs. a facile WC universe. Some good suggestions to help harmonize the basic conflict have already been made, and I'm sure we can come up with others. As for the "Armada" statement itself, Earthworm's suggestion of a different standard of travel is a very interesting one. Alternatively, "something" could have happened between 2664 (the time of the statement) and 2669 (the time of WC3) that "opened up" the space.