based on time spent, it's:
1. HoT
2. EoD
3. PoF
However, HoT forced me to spend a huge amount of time due to it's difficult navigation, enemies, and story locked behind masteries. For my time spend in EoD, I did so willingly chasing after optional achievements/collections. As for PoF, story was good, but the maps feels so boring that I dropped it as soon as finishing the main story. So I would say EoD is my favorite expansion