Master's No Longer Best for DE Farming
With the matchmaking change to increase your chances of finding someone the same town hall level as you, it is now easier for TH9's and 10's to find other 9's and 10's, despite their trophy range.
For this reason, I recommend avoiding Master's League. The old narrative was 'the higher your trophies, the more DE you will find'. While that might still be true, Crystal and even Gold leagues can be just as good for DE since the matchmaking update. Bases are, on average, weaker and therefore easier to penetrate for DE.
Thoughts? Where have you been successful farming? What are you using for DE farming?