Efficiency broke recently. It's fixed internally and you should see the fix soon, but I'm not sure when.
You should be able to see constant shield regeneration from the nanites. The increments on the shield bar are not as granular as your shield strength, so it can be healing when you aren't seeing movement. The combination of the shield pop mechanic and needing to constantly take damage makes it hard to see what's happening. You can mouseover the shield indicatior and see it increasing.
Health regen happens in chunks. Each time you regen a chunk of health, the nanites will increase that chunk. It's not steady like the shield regen, but I'm seeing it happen in combat.
That said, it may still be providing less benefit than intended. I'll take a look at it.
Thank You for taking the time to respond, and further investigate!