Fortunately there are now so many bike startups in Singapore that you have a wide choice to pick from, and all of them are currently free. I went to the market yesterday with my mother in law, her riding a Mobike and me an Ofo, both checked out with my account.
Mobike seems the best run although I agree with the low seat problem (which is less of an issue in Asia). However, there are 3-4 different models at any one time so I suspect the company will iterate towards different models for different markets, including in size. Some of the engineering on the newer prototypes is quite interesting, and copied a few months later by Ofo, which seems to be the other company with actually active management (after a disastrous start with non-GPS-tracked bikes which were routinely "retired" by users).
As for bad parking, it is a function of enforcement. In Singapore, the companies are fined a substantial amount per bike if the government has to come and clear them. So there is apparently a sub half hour pickup time for most if you report it parked incorrectly (e.g. in a bus lane). It sounds like Australian cities have not yet put their act together in that respect. Fine the companies $500 per bike dropped in a creek and watch the problem disappear...