I have a firm belief that it also has a lot to do with manufacturing inconsistencies in kanger products. Been like this with Kanger wince day 1, not just with the Subtanks.
That could be possible as I didn't buy any of the first run Subtank Minis... but I've owned 4 authentic Subtank Minis (3 were with the single airflow control, 1 with dual, all 4 with the brown peek insulator) and never had trouble with any of them.
These days I'm liking the dual coil, higher airflow RTAs more, as the Subtank is deceptive with a large airflow intake on the outside but a not so large airflow opening in the RBA head (that has to pass through the bottom of the coil head -- and the "improved" dual airflow barely makes a noticeable difference) -- But maybe I'll become a fan all over again as I get into TC vaping. I hardly use mine anymore but it was my ADVer for 3-4 months, and my girlfriend still uses hers daily. These Subtank Minis (as well as a few replacement RBAs and replacement airflow control bases) have been very consistent, reliable devices for us.
Like I said, I didn't buy any at launch or that close to it. Kanger isn't the only company to rush the release only to put out an improved version shortly after, and while the rushing release part isn't favorable, it's at least nice that they listen to and respond to consumer issues.
We also own four Kboxes and I only had issues with one of them; which Kanger quickly fixed for me without question or hesitation (got it back within 5 days of sending it in). I love the Kboxes and they're my go-to mods for a day at work and I prefer them over my Istick 50W.I actually broke the cage section of one of my Subtanks (completely my fault, nothing wrong with the device) and they fixed that too even though it really shouldn't have been covered by warranty -- so in my experience their customer and warranty service is prompt and exceptional.
So, maybe I've just gotten really lucky, but 7 out of 8 products Kangertech products I've purchased have been very reliable and the one that wasn't was fixed promptly... So my personal experience would allow me to buy any future Kanger products that I may be interested in with a fairly high level of confidence (just maybe not by pre-order or at launch), and I would recommend them to anyone that asks based on my experience with product and CS reliability.