We don't! The UV is going to go up over the time that you hold the property anyway (at least you'd hope it would - otherwise why buy it?)
If land tax is a concern to you then either spread your investing around across other states or buy units / townhouses with low land component, or both.
Council or government valuations often bear no resemblence to market value. Obviously a higher valuation means higher possible land tax, assuming you exceed the relevant thresholds. If that is the case, it then might have an impact on your numbers if a prospective purchase increases your land tax bill.
How material that is going to be, will depend on your existing land holdings in that state/territory and the marginal impact on UV of the new purchase.
Otherwise, its irrelevant.
Edit: I had a look at ACT land tax rates. They seem awefully expensive. Am I missing something?