With including stops at all the train stations from Waikanae to Takapuna Road, driving (No time for passenger pick-ups) google gives 1hr 7mins to Petone Rec.
The two trains combined appear to be about 30mins longer (Including the walk to Petone Rec 20mins), only 10mins longer without the walk.
But a bus is going to have to stop at all of those as well. Remeber we're not comparing with a car here.
A little co-ordination so the additional Hutt trains run straight after Jville and Coast arrivals wouldn't be too hard.
It would need Tranzmetro to buy into a stadium ticket that covered all legs of the journey.
Also. The walk down Jackson street is a million times better than the concourse. Particularly in a northerly.