Keepers in this game have a serious issue with training their creatures. They usually only have a small handful of high level troops and they're the ones that automatically train. Half their creature pool is taken up by low level trolls/biles/locks. They don't react well to traversing lava either. Just convert their bridge when they build it and sell it. Attack over. The end. Everybody go home. We'll try again in five minutes.
If you can find a way around those problems, it'll definitely spike the difficulty of the game a bit.