I haven't played this yet on defense - I suspect it will be tough. Attackers get so many troops, I don't see how the defenders can kill enough to win given their low numbers and seeming reliance on pitch to do the dirty work.
I think you should let any who try to tunnel discover the ways you attempt to defeat their efforts on their own. Telling them in the writeup kind of ruins the whole idea of having those diversionary tactics in place. I'm not big on the use of tunnelers (have yet to see a Siege That! where it helped me), but why tell people what NOT to do? The fun is finding out on your own ;)
Dogs seem very tricky to use - most of them attacked the defenders instead of me = )
I think you should tone down the attacking force a tad. Right now, it was way to easy to Siege with what you gave me.