It really depends on your Parts. If you have many large and irregular shapes it is unlikely that you can dramatically improve your efficiency. However, if you are nesting regular parts or if you have small parts to fill the gaps, it is possible to achieve 90+% utilisation. Also if you do not use up the entire plate you will get a lower utilisation.
You may want to look at grouping your plasma cuts together and your marking cuts together across the nest. Under the Process tab, there’s an option of the process to be carried across the nest instead of part by part. This saves the number of times you have to change torch or the torch settings. The side effect is that it will generate a couple of longer rapids – depending on your machine, this may be less time than having the machine switch torch.