I think CVE-2011-3414 is not really fixed in mono, the "secure" hash still allows to trivially create infinite collisions.
You attempted to fix it in this commit:
the algorithm looks like DJB31A were collisions can be created from any string with bytes x and y by changing them to x - 1 and y + 31
(to get infinite number of collisions you need to adapt that for integer overflows)
this method is completely independent of the seed.
note that python made a similar mistake in their fix, see http://bugs.python.org/issue14621
a proposed solution is to use siphash
the seed does determine when the overflow occurs, which you need to know it to create more collisions
but as with this algorithm the integers overflows after 6-15 iterations you can very likely just guess this from the response times of the server in very few tries.