There are many factors to remember when considering this apparent mis-match. The Toblakai have been imprisoned in the Azath for tens of thousands of years, so they're more than a little dis-orientated. Corlo is using all of his considerable High Mockra talent to distract them, and Ublala is also helping Iron Bars. He is also considered second only to Skinner within the Crimson Guard too, and we have had hints that Skinner is almost on a level with Dassem Ultor/Rake/Greymane etc. Then consider how easily Iron Bars disposed of Rhulad after the Edur leader had cut his way almost single-handedly through most of the Lether army. He very nearly loses several times despite these factors, too...
As for Silchas... well, he was the Supreme Commander of the Andii forces when they came through into the Malazan realm so many years ago - and is superior to Rake, allegedly. He features prominantly in
Reaper's Gale according to people who've got advanced copies, so we shouldn't have to wait too long to find out much more about him