We did Wolf/Darwin/Wolf. There are a lot of dives sitting and watching the hammerheads. We only saw Whale Sharks at Darwin, but on two of the 4 dives and right up close
The trip prior to use did not see Whale Sharks.
We had a greater variety of dives at Wolf and there is more to see than sharks!
Wolf Day: Shark Bay, Landslide, Landslide, Shark Bay North
Darwin: Darwin Arch x 4 times
Wolf Day: Shark Bay, Landslide, Caves, Bat Fish
For me (and I like sharks) this was a good mix, but if I was assured of seeing Whale Sharks on a second day in Darwin it would be a difficult choice.
The trip back from Darwin to the 'main' island is long so I would expect this may impact on diving the following day. We did Wolf to Vicente Roca and arrived in time to do our first morning dive, I don't think this would not be viable from Darwin. Hence some trips miss Vicente Roca and a chance to see the Mola Mola - the water is cold.