I've been using an LTC pool as a backup pool, and have had no issues (hashrate/payout are near what is expected), and it has switched back and forth several times.
I did a little side-by-side testing last night and can also confirm that the new block messages on the backup pool (LTC) did not show up while on middlecoin.
Kind of odd, I wonder why it is advised against by the cgminer guy.
tricky because I think good settings for a fast coin maybe not so good for a slower one, I'm still tinkering.
lowering -E may help
The one setting that made a significant difference back when I was on DGC for a while was intensity. Of course this lowers your overall hash too, but i18 instead of i19/20 made a notable change.