[This post is mostly in regard to WvW]
First of all, let's take a brief look back at the history.
Before Heart of Thorn, the most popular way to deal with incoming conditions in a organized group fight was at the beginning cleansing. Practically every single Guardian and Warrior player I knew was equipped with Runes of the Soldier (nowadays, Trooper) and slotted with at least two or three Shout skills. Then, people realized that if one could reach a certain percentage of condition duration reduction, incoming conditions just could not get applied at all. With proper equipment and Purging Flame, it was possible to reach 90% or even higher peak duration reduction, resulting in practice immunity to any incoming condition pressure.
With the release of Heart of Thorn though, Resistance was introduced and Revenant with Legendary Demon Stance soon became the go-to anti-condition setup. Purging Flame quickly lost favor, with the majority of the Guardian players back then I knew would instead slot two utility slots for group Stability ('Stand Your Ground!' & Hallowed Ground; or heck even sometimes three with Fragments of Faith) and one for personal mobility (Meditation) or group Protection ('Hold the Line!').
However, with Path of Fire, the sheer scale of boon corruption brought up by Scourge demands more active condition management, that is, constant cleansing. Firebrand with its Tome of Resolve and Mantra of Lore, and then after several reworks, Scrapper, became the dominant force against conditions. Purging Flame is still picked against serious condition pressure, but more often then not, some other utility skill would be more preferred, than 3 conditions cleansed on a 35 cooldown plus little to no help from the duration reduction against consistently applied incoming and stacking conditions.
To make Purging Flame back on par with other condition management skills, certain changes must be done. One I can immediately come up with, is to replace the group reduction effect with group Resistance, one of the least accessed boon across all professions. The cooldown could also be adjusted in accordance with the duration of the boon.