Clarification: Don't bother farming for the BSW set anymore if you are a Magplar. The proc chance and increase in spell damage are both being nerfed in the Morrowind update (as per PTS patch notes 3.0.3, it may change again). ZoS doesn't like it when one set becomes THE "go-to" for all classes, so they tend to tune the set values until there are other viable choices.

The specific challenge for Magplars is that they only have one class skill which does flame damage (Burning light and morphs), so you'd have to rely on destruction staff (Wall of Elements) and/or light attacks with a flame damage enchant to proc the BSW set. However, once your target is at 25% or lower, you should be channeling your Radiant Destruction execute continuously - anything else is a DPS loss - and that does not do any flame damage. That means your BSW 5th piece bonus is going to be useless for about 20% of the fight (the execute phase goes relatively fast if others also have executes). BSW may still be appropriate for magDKs - not sure about any other classes.