This question was posted a couple of days ago on the Steam forums, but despite there being  official responses to other enquiries, as of this time, Neocore have not responded.

Unlike previous DLCs that are purchased, I have discovered that the recent Herald Cherub DLC when purchased is specific to just one character. So, if you wish to use it on more characters you have to purchase it for each one.

Is this working as intended and is an attempt 'to slip it in under the radar' or is this a bug?