Well, it's not really meant to be a snowshoeing trail, but on this day, it was. Also, it should be noted that it says 7.1 miles point to point here; I don't know what they're talking about, but it's about 5 miles from the Starvation Ridge trailhead (where the Mt Defiance trail starts-same area) to the top of Defiance's summit.
Anyway, it's a steep trail that's good training for the legs. Here in winter, at about the 3800 foot mark, I found awesome snow drifts to climb over and through. Great snowshoeing. I cut a straight line to the summit; the marked trail disappeared (ribbons blown away by the wind).
Took me a little less than 3 hours to get to the top; shorter in the summer, when the snow is gone. The steepness of the trail is good training for mountaineering, and plan on good views of St helens, Adams and Rainier if the weather is clear. Pack differing layers, food, and water, and enjoy the burn!