To start, I understand you gain bonus progress in Heresy activities, but I just did a GM nightfall which had about 10 Banes spawn. Of which I killed at least 6, but I gained only 3% progress.
Given banes only spawn in harder content, and only about 10-12 spawn per run, your in for a hefty grind. Even of the bonus progress is 2x, that's still at least 10 master runs of the nether or court. That's not even considering if you fail, or if it even counts teammate kills as progress for you.
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Its a long term goal and typically not something done in an afternoon of gaming but, you could. 3% per run.. get grinding those 33 runs. Most people are likely close to completing if they have been playing all season. If you havn't been playing the seasonal content you will be behind and need to put on those grinding pants to catch up.