I'm not quite sure if its' meant to be a ranged, melee, or something focused set... I'd probably harmonize (hehe) that a bit more.
That being said, what if your "stacks" were like,
"This attack builds a stack of Dissonance. When you reach 3 stacks of Dissonance, your next attack releases a cacophony of sonic energy around your target, stunning (mag 2) and reducing the resistance to all damage of nearby enemies." Remove the stack consuming on all abilities except at cast 4. USe the graphic of music notes from Sirens ^_^
Then you can start removing some of the -res in the attacks in favor of some other effects.
Scream (should actually be Shriek at moderate damage), Howl, Shout can keep theirs. Remove it from the melee attacks. Turn Harmonize into +deal extra damage as energy, +3 stacks (Copying Water blast for stacks, Martial for +damage). Would to see Sonic boom as a -Resist variant of Psychic Shockwave, personally.
Something like this would give you
Synergy with Stun
A hybrid between Melee/Ranged
Harmonize would benefit from its own abilities' -Resist
Anyways, the issue I have with Sonic is that it inherently suffers from reduced damage due to its effect (a tax, if you will); as such, it does innately lower damage... which works well on sets that are not about doing damage. Since a Dominator is very much a 'be one of the ones doing damage' AT, it'll probably work out as well as Sonic on blaster (hint: it doesnt 😞 )