I've been doing Extremes and Savage since Stormblood. I think that the difficulty level for the Extremes has been roughly same from SB through EW. Extremes usually have 1 make or break mechanic while the rest is more smooth sailing. As for seeing less extreme fight listings in PF over time, maybe it's because more people are actively doing savage and ultimates? In the past, ultimates were almost exclusively done in statics, but their listing count has jumped. This is just my experience and observation though as I do not have any metrics to back up what I'm saying.