Fun little game! I would say maybe lower the health on the enemies but up the number of them? It's more satisfying to take out lots of enemies rather than end up wailing on a few enemies over and over waiting for them to die :)
Balancing is a dread BUT look at games in the same genera, a lot of the time the fun comes from unbalanced stuff, in Roguelikes that random unbalanced nature is good fun! I love that one run of Binding of Issac I can be a god, the next I can be total crap haha.
Keep up the good work! :)