Hmm...how is your opponent supposed to counter being permanently silenced aside from happening to have a Permanent/Creature on the field ahead of time to stop Dream Hawk?
Do Dream Hawk's counters continue to decrease by 1 each turn regardless of its ability being used that turn?
Can Dream Bird's ability be used to counter the spell, Silence?
While I do feel permanent silence is extremely powerful, you have to take at least five turns to set it up.
It really only takes 3.
Turn 1: Play quanta, etc., play Dream Hawk. Considering its effect works just like Phase Shield, one counter is removed when you end your turn.
Opponent's turn: Free to act.
Turn 2: Activate its effect, remove one counter. End turn, remove another counter.
Opponent's turn: Free to act.
Turn 3: Activate its effect or just let the turn pass, remove the last counter.
Opponent's turn: Silenced.