The times quoted, 7 and 12 minutes for two different trips from Dorcas St to Flinders St Station, seem to be pretty normal for travelling that distance in the inner-city. They don't seem strange at all, and given that they're both under 15 minutes, they definitely can't be taking 15 minutes longer than before
I've walked along there a lot in the last few weeks - the bike lane has been very busy with bikes, and it is wonderful having the whole bridge for pedestrians.
I did notice, however, that sometimes the light sequence for the pedestrian light near the tramstop is a bit too short, so that with only one lane filtering into the 'holding area' between these two sets of lights (at either end of the station), there actually isn't enough time for the whole space to fill up with cars. That means that when the Flinders St lights go green, there are fewer cars waiting to get through.
This will of course make it a bit longer to travel this section, but the most minor of signalling tweaks (the few times I witnessed this it would have needed an extra 5-6 seconds of green on that traffic light) would solve that problem.
Still a cyclist, albeit one who never rides any more....