Personally, I regard it as a DA mechanism, because the trigger performs two actions of cocking and releasing. I recognize that it starts off partially cocked, and that is why it lighter than conventional DA mechanisms, but it still performs both functions of a DA mechanism. Creating a new category of "striker" could be useful, but striker-fired pistols have a good bit of variation in how much pre-cock is present, too. Mostly I think that understanding it is more important than shoe-horning it into a conventional classification.
I agree with your conclusion that it needs a holster, but the length of pull makes the comparison to a cocked revolver (or unlocked 1911) less than fully accurate.Would you walk around with a cocked SAA or S&W Model 66 in your pocket? That is exactly what your are doing if you carry a Glock in your pocket without a holster protecting the trigger.