Oh, and if something maximising entropy is a valid optimisation process, then surely everything is an optimisation process and the term becomes useless?

Not really. A salt crystal is not an optimisation process - at least not on conventional timescales. However, certainly optimisation is a widespread, "universal" phenomena - driving most change in the universe and all self-organising systems - including biological ones.

Optimisation processes lead (locally) away from maximal entropy, not towards it, right?

That description certainly fits a star. The star is locally ordered (it's a big, dense ball of matter), but it creates global disorder - in the form of heat and radiation.

However, I don't think there is a general statement you can make about what optimisation processes do to "local" entropy levels. For a counter-example, consider gas expanding to fill a box. That is surely an optimisation process, and we know what solution it will converge on. However, there is no associated "optimising agent" using a heat pump to perform work to execute the task - and consequently there are not really any "local" increases in entropy occurring.