The Sonicors nuts. I potato-ed it, and with 180% multi shot and Blast damage, I don't really need to aim. Just wave it in the general direction of the enemy and press right trigger and watch the rag-dolling and explosions.
Sonicor is a lot of fun, and I put some work into it. Unfortunately, it isn't really viable late game, except for crowd control purposes. It simply doesn't do enough damage.
A question about damage types (which I've only just read into). Wiki says one of the benefits of blast is knockdown. Given the Sonicor has innate rag-doll, is it better to go for a different damage type?I here corrosives the go, but looking at how everything works that may require some Forma. Hmmm....
Damage types are tricky. Recommend looking at the damage 2.0 page on the wiki.
http://warframe.wikia.com/wiki/Damage_2.0
It really comes down to which damage types are effective against the most (or the toughest) enemies, and I think most people have settled on Viral, Viral and Heat, or Viral and Radiation depending on how many mod slots you have to work with. That said, I've gotten some milage out of corrosive and blast as well.
I think it's important to think less about the proc effect than it is to think about how the raw damage of different elemental types works against different enemies, especially on a gun like the Sonicor, with its innate blast-like ability.