Simplest way to convert 78 VDC to 3.3 VDC?
According to this, the ESP8266 can draw up to 215mA when transmitting, so you need about 0.7W supply capability to not have to worry about what the chip is doing. 

There are a number of switcher chips (including output transistor) that will work with ~100VDC input. The LM5018 is one such possibility (I've used its lower-current little brother the LM5019). You could roll your own using an offline switcher circuit with internal or external switch- provided the ULVO does not cause problems. 

Another possibility (especially if parts cost is the most important concern) is to make a linear pre-regulator and use a lower voltage switch regulator. For example, if you used a MC34063 with an input voltage of 35V you would have to drop 43 volts at about 20mA, or about 0.9W when transmitting (and much less when not). The linear preregulator could be as simple as a zener diode, a resistor and a BJT. 

For much lower currents, and thus probably not suitable here, one very elegant approach that could work might be to put a shunt regulator in series with the LEDs. The maximum current you could draw would be the LED string current. So if the LEDs drew 300mA the shunt regulator would dissipate about 1W with the ESP8266 chip in standby. However it would stop working when the LEDs were turned off, which I suspect would not be useful.