Excellent guide, but it is definatley geared to defenders and corruptors as opposed to blasters. I have a lvl 50 Sonic/Elec blaster on Justice and would like to add my 2 cents.
I was only lvl 10 when I9 came out, so all of my decisions have been based around IOs and do not refelct previous issues.
Shriek is an excellent power, quick recharge makes it an effective "proc gun" if you so choose, with set IOs you can easily get the damage maxed, the recharge more than adequate, some end reduction and plenty of Acc, and still have room for a "chance to build-up"
Scream is your primary damage dealer, not in a single activation, but long term. Since you will be firing off shriek and sscream all the time you will be stacking the resist debuffs so the damage is going to be nice.
Howl is also a mainstay of this set. As you point out, the damage is not the greatest, but it does debuff a lot of enemies at once. This is one of my primary powers when in a team, i usually lead off with this to start a fight and re-apply as it comes up.
SIren's song is pure gold for a blaster. Blaster tend to have an easier time soloing than a defender, and at least for sonic/* this is a primary reason. With only 4 slots you can keep a spawn asleep permanently, waking up only your target that you are trying to kill, rinse and repeat. But a defender gets this power much later, making it more attractive to a blaster.
Shockwave is not a power I have used, like you I am not a fan of knockback (except in some melee powers for blasters).
Amplify is good, but I always take build-up before Amplify (as do most blasters I know) but I do find a place for amplify at some point.
Screech is another key weapon in the sonic arsenal. Use your cone sleep, then screech to stun a target and you can kill whole spawns with almost no attacks coming your way.
Dreadful Wail is a good nuke. As you described, it is an absolute necessity for a blaster, nice for a corruptor, and marginal for a defender.
I enjoyed your guide, and want to say thank you for maiking it, there are far too few sonics out there. I just wanted to add my observations as a blaster.
