I've been having the exact same issue, but have mostly resigned to the notion that the server mode wallet is not capable of producing getwork fast enough for my antminers to solo mine.  I don't know that I'm right in that assessment, but in the research I've done, it's the best I've come up with so far.  I think also stratum might be useful for just such occasions, which can only be setup as a pool server, so far as I know.

Also, does anyone know of a way to swap out the pool details for multiple units in one go?  It's a pain in the ass logging into a series of units and repeating the same commands over and over, just curious if there was a multi-ant controller of some sort I should be aware of.