[caliaca]

Which class has currently no way of dealing with Silence and can't act with it?

Evoker (Whispering Cant only works for mage base spells and increases their costs by a lot), Rune Mage, Tactician, Magic oriented Ghosts, Hexer can only inflict silence not remove it, Ranger is another, Priest/LB/Aqua cannot remove etacof thus silence will stick.

All in all, currently you are subjected to slotting Heron Feather always as it's become pretty much mandatory for magic builds.

On the ranger example, they have a ton of moves and skills that are not affected by it including one of their heals. They're generally hampered worse by Immob. 
Whispering cant allows you to still act with stuff, and I'm not sure counting etacof is really fair in this regard.