Looking at this two pictures, I cannot decide what's worse. The design or the assembly...
I've seen worse. Sure the hand soldering isn't the neatest but the board clearances seem mostly respectable, it uses a fused IEC connector (or maybe switched - I can't tell. Check the fuse rating).
The main thing I notice is that the permanent live track runs close to the connector earth connection, and rather more importantly, the Earth connection doesn't seem to go anywhere, just to a couple of plated through holes on the PCB. Without seeing the head and case It's impossible to say whether it's a Class II double insulated product or not. If not, then there should certainly be earth wire connections to the case, if it is metal, and any exposed metalwork on the head (I'm not familiar with the T12 hot-air).
Regarding permanent live going straight to the element in the head (and the Triac in the Neutral), it's debatable, I suppose ideally it would be in the Live feed, but Triacs can fail short circuit too, and it puts less dielectric stress on what may or may not be a high quality opto.
The safely, or not, mainly rests in the design of the head and whether there is some form of safe connector between to two (or whether it is direct wired).
EDIT: From your above post, it sounds as if you definitely have a problem with connector safety and non-earthed metal case. The second is easy, the first not so much (unless you can permanently secure the plug).
If it has a connection in the head cable that goes to the head metalwork then you should definitely earth it. Otherwise, if it doesn't pass an insulation test at 500V, then it is unsafe to use anyway (regardless of whether it breaks it).