This is were I very respectfully have to say (and this is my own personal experience) that I've yet to have one single issue with the purple Efests. Right now I have a .31 ohm Atlantis coil in a Melo on an IPV3 at 48 watts and I've yet to have anything even remotely scary happen. I still have a few mechs which I use sparingly, but even when I used them heavily, mostly with .5 ohm Atlantis coils, I never had any issues. Everybody I work with uses the same batteries and no one really builds below .4, but again, none of them have had any scary experiences. So far it's been day in, day out like normal. We all respect our batteries, too, though. I guess I'm blessed in that so far everything has gone exactly as it should. That doesn't mean bad things couldn't happen, though, and I'm acutely aware of that. But, speaking strictly from what I've experienced on a day-to-day basis, in the field, the purple Efests never really raised any concerns for me.
THAT BEING SAID, Baditude is a local legend around here, a tried-and-true experienced vaper with infinitely more vast knowledge than me, and if it came down to you reading my post or his post, I'd err on the side of caution and go with Baditude. He's our Miyagi for a reason.
EDIT: Also, this link is highly referenced at work:
Watts/Volts/Amps/Ohms conversion calculator