I'm using microcore 2.1. I have noticed that dc is no longer present as an applet in busybox.
Yet there is still a dangling symlink from /usr/bin/dc to busybox.
I saw there is a a gnu bc and dc extension that can be used instead. Still I vote for having dc in busybox. The reason is because busybox dc can be used to provide number arithmetic to shell scripts, a quite basic functionality as I see it.