Wow, I don't really use dictation so I never noticed it, but the bug definitely is there.
This is what happens when you use dictation, and close it with a split keyboard
This is how it should look normally:
I actually think it looks cool when it is transparent over the translucent background of spotlight, but it still isn't normal behavior lol.
They really need to dedicate an entire x.2 or x.3 update to major performance enhancements and bug fixes for iPad only, because they really left behind the iPad in iOS 7, performance has been screwed up for a long time. Lag was still definitely there on the once flagship iPad Air and Retina Mini even on 7.1.2 which was talked about as a quite stable version. Lots and lots of slop needs to be cleaned out of the iPad experience ASAP.