Those are not dashes. Dashes are longer and look like this: —(em dash) and –(en dash).
Hyphens are shorter, like this: -. They're used, among other things, to join words in uncommon contexts, so the reader understands that the words are to be understood as components of a phrase.
In your example the adverb phrase all too frequently has its ordinary construction and it occurs in an ordinary context, following the clause it modifies. Consequently the phrase should not be hyphenated—joined with hyphens.
But if you wanted to use the same phrase in an unusual context you should hyphenate it—for instance, if you wanted to use the phrase as a noun denoting something that happens more often than you like
Three more complaints about Fred? Add that to the all-too-frequently list, and maybe that alongside the absences and the missed deadlines will persuade Bob to get him transferred to another department.