I've been searching everywhere to find the frequency of Devanagari's signs (including the sign in a conjunct) in a typical Sanskrit text. I found the frequency of Devanagari conjuncts here and there are a million sites on the word frequency of Sanskrit but no luck for particular signs. Any help would be greatly appreciated.
Fortunately, the very same source (Whitney's grammar) used in your conjunct consonants link also gives the frequencies of individual phonemes, which I will take to be an acceptable proxy for non-conjunct glyphs. If you are really interested in the frequency of non-conjunct glyphs but not the phonemes, then I can't help, sorry.
Here is the relevant page.