Charges are not considered "buffs"?

According to this post way back in November, the passive skill nodes which give "Buff Duration" do not effect the endurance charges or frenzy or anything like that, and so the one skill (Enduring Cry) which I thought of as a "buff" is uneffected.

Is this still the case? Why is it the case at all? Does anyone use these passive nodes for only increased curse time and phase run?

I'm pretty certain this is still the case. My DoT ranger uses them for Poison Arrow, Puncture, Phase Run, and Bear Trap. I've got Hex Master, otherwise the curse time would be nice too.

So is there any way currently to increase the duration of charges from Frenzy or Enduring Cry?

For each type of charge there are 2 duration nodes and 1 utility node.

Look for "+1 maximum endurance charges" keystones, each connects to another node that modifies how your charges work somehow. You can get an added 20% duration for 1 skillpoint.

Builds that use charges encourage you to stay mobile. You can teach yourself to maintain 5-stack endurance without the duration nodes. Just gotta keep moving.

The only other way besides the duration nodes that I know of are to play maps with "Players are cursed with Temporal Chains". Hint: this is not a good way to do it.