I was having trouble getting Tanto to deep sleep on A3, actually. I found that if I rebooted and did nothing, it would never deep sleep. But after I downloaded Voltage Control and fiddled around a little, it started deep sleeping. Every time I rebooted, I would have to go into Voltage Control and apply settings before it would deep sleep again.
Not really a scientific sample size, I know, so it could just be superstition, but that was my experience. I'm waiting a bit before I try A4 so can't offer any insight there.