I agree with you to a certain extent. However you don't have to look past trance events such as Slinky which massed approx 5000 people plus Two Tribes, Gatecrasher's and many others we have experienced this year and other events years before which thousands of people have gone to.
But these are superclub names and events which are always gonna attract people.
Huse events also attract lots of people like as you mentione DHN'F, N&U etc.
I think one reason why house events may be more popular could be that in general tickets seem to be cheaper? (correct me if I'm wrong). Perhaps this is because we have so much quality and talented local talent which we support without having to or needing to see so many internationals, however they are much appreciated when they arrive to our shores!! eg. Deep Hard N Funky was $25 with an early ticket versus $50 for Gatecrasher.
However, NZ also has some wicked trance dj's also that never fail to impress us on a regular basis.
There seems to be a lot more local house dj's than trance dj's.
Just a thought