The aura highlight widget is not working on priest for dispelling magic debuffs. It seems to work on a shaman with Purge.
Needless to say this needs checked on the other offensive dispelling able classes.

It used to work when i first started using the addon, but for quite a few revisions now it has stopped working. Was hoping this would get fixed, which is the reason i didn't report until now.

Priest:

Shaman:

That's a bug I would say in the aura informtion in Cata. I just checked.

As I Priest, the buff is reported as not dispellable by the WoW API:

As a Shaman, it's shown as dispellable:

Not sure what can be done regarding this. I don't have a good idea.

An idea is to have a fail safe: all priests can dispel magic on enemies, you don't need a certain talent for that. I guess just check if priest and magic type aura then act as if aura is dispellable?

LE: also i guess report this as a bug to Blizzard? it was working in the past

That would work, but as far as I know debuffs on Classic do not have a type information (like magic, poison, and so on). This information should only be available on Retail.

How is your addon detecting the type of a buff/debuff? It's colorizing the edges based on type of debuff. I'm confused about your statement above. In the report snippets, the aura is literally colored blue for magic.
LE: for the purposes of this bug report, aren't those auras... BUFFS?

I knew it was giving the type of aura:

Seems they do give the debuff type on Classic.

That ... makes sense. I think I need to take a closer look. Maybe I remember wrong :(

You are right:

TP - DEBUG: Aura: Mondfeuer => ID: 8921 , Type: Magic  , Effect: HARMFUL
TP - DEBUG: Aura: Krallenhieb => ID: 1822 , Type: nil  , Effect: HARMFUL
TP - DEBUG: Aura: Krallenhieb => ID: 1822 , Type: nil  , Effect: HARMFUL
TP - DEBUG: Aura: Zerfetzen => ID: 1079 , Type: nil  , Effect: HARMFUL
TP - DEBUG: Aura: Zerfetzen => ID: 1079 , Type: nil  , Effect: HARMFUL
TP - DEBUG: Aura: Nachwachsen => ID: 8936 , Type: Magic  , Effect: HELPFUL

I should also have seen that earlier as there is an option (even in Classic) to show enemy magic buffs ...

As an update: in mop prepatch now DKs have highlight active on enemy magic buffs :D
I guess Blizzard API returns are completely unreliable and you need an internal check for that feature.

I am also working on a fix for Priests if this still does not work in Mists.

Seems it shows as dispellable in MoP prepatch for priests. The issue might be that it is showing as dispellable for every class. I can check if you give me a few minutes.

Sure, no hurry. I am currently working on enabling the Quest widget for Mists as there are now Quest tooltips. I will finish this first anyway.

So it seems priest shows highlights, paladins dont (as intended), hunters do (as intended), DKs do (seems in MoP you glyph Icy Touch and you can dispel offensive)

I guess all is working as intended!