It felt like it needed a full restart anyhow 
After changing the (empty) file, and rebooting, I'm now seeing load numbers that still bounces around a bit, while Memory Usage is down to 19.3% (with a few more lists added, now up on 631k domains.
What does the NXDOMAIN actually do, mainly in concerns of privacy?
Also, in case of more testing for you guys, then the Pre-4.0 ran the approx. 3mill domains just fine, with a fine memory and load usage (load was usually, as mentioned before, near 0).
In either case, seems this has fixed the issue for now, so I'll again thank you for your help and assistance.
I'll slowly try to add more domains again, and see how it turns out.
Alternatively I suppose I could just take a look at what actually goes on, and just individually blacklist what I do not like seeing - which might really be the smarter approach (not to mention faster), as compared to just blocking what looks to be about 1 million random porn sites (judging by the list called "top1m.list"). 
Edit:
I do however still have 'issues' with this not looking just right, is that just me, or is it something I'm missing?
