Usually it is recommended to put resistors in parallel to each diode like this:
It is supposed that the resistors will equalize leackage currents and make the voltage drop more even.
However, I doubt that. And that's why: diode I-V curve looks like this:
All diodes will share the same leakage current. And if the voltage is low it CAN be distributed unevenly. But it is not a problem until any diode will aproach to the breaking point. At this point the curent will go higher for all of the diodes. And all diodes will have a voltage drop near to its breaking point (V1, V2 and V3 on my ugly drawing).
So even different diodes (like 200V plus 1000V to have about 1200V of reverse voltage) should work well in reverse without any additional resistors. The only thing should be considered is the reverse leakage current of the most leaky diode multiplied to the highest breakdown voltage which in turn can make the last one to melt.
So is there anything I missed?