the diode/resistor is to allow gate charge to drain away and allow the FET to turn off fully. A buffered logic output *should* pull down hard enough to do so, but I have experience of them not doing so...

If you have a test meter, what is the voltage swing at the gate? If you disconnect the BOB does the laser go off? It could be a dodgy FET of course... or reversed so the source-drain diode is conducting... (I know you've probably checked that, but I've lost count of the number of times I have checked and doubled checked and *still* managed to get it back to front!)