I have an AFF A700, and a FAS 9000 with only ESX hosts attached running Ontap 9.4P1. The A700 has all efficiency functions enabled, the FAS9000 is only using inline compression/compaction. Both arrays are delivering block level services via FC, with no filer protocols in use.
Some guests have data that has already been significantly compressed/deduped, and for these even 1.15:1 is reasonable.
On some other guests I have seen 2.5:1 just with compression/compaction.
Those numbers are without snapshots or cloning.
I look at efficiency with regard to placing things on the flash or spinning disk unit. If it doesn't need high IOPS/low latency, and it isn't very efficient, it goes on spinning disks.
I can report from "the field" that we have deduplication and compresssion ratios between 1,52 to 3,54. It depends on the data. If you have a "normal" VMWare Environment with DC,Exchange, FileServer, SQL, and so on, an Efficiency Ratio of 2:1 is absolutly realistic. If you have Medical Data like PACS it will be unrealistic.