[Autumn]

Silence is an inherently stronger status effect than Immobilize or Clumsy, but both Immobilize and Clumsy cannot be fought against with item slots and their specific counters come from either your item belt or specific skills that cure those conditions.

Silence on the other hand has a plethora of options that were introduced in plenty to help combat the absolute strength of the status that it had back when 3 duration was it's standard, and it was available from far more sources. Understand that Silence was nerfed already.

Heron Feather exists as the 'mandatory inventory slot' for those classes that cannot inwardly deal with silence on their own, those being Rune Magician, Performer, Dark Bard, Grand Summoner, Shapeshifter and the caster variants of Ranger and Tactician.

In it's best cases, silence is just an inconvenience to a good half of the caster set of classes, a momentum trade akin to Knockdown or increased FP costs to certain abilities (which seems fair to me personally)

In it's worst cases, Silence has the capability of ending a fight where it is applied, even though Heron Feather is used to partially avoid these major cases, I think that silence could stand to see immunities in play on an underutilized item, that being the beloved Throatopener, which I believe should grant a 2 round immunity to silence upon curing it,  similarly to Silent Prayer.

Though the OP refers to nerfing silence in a very exaggerated way, I believe the 'peak' of silence's effectiveness justifies some sort of counterbalance to in most part that effect.