On the offchance it helps someone, here's a couple of things i've found with the Wraith.
I was getting dry hits literally every second or third puff so I raised the coil a little more than the original couple of mm's I had it set at and put a very slightly thicker wick in. That helped.
After a couple of days, juice stopped entering the atty, no matter how much I squeezed, the best i got was a trickle. If you get this simply take the atty off, remove the juice bottle and give it a really good blow through (from both ends) until you can see clearly through the hole. That sorts that out.
This really is an outstanding piece of kit, although i do worry about how spongey the bottle gets so i'm after replacement bottles just in case.