Server 2012 AD-DS Setup Fails (Microsoft.Directory.Services.Deployment.DeepTasks.DeepTasks not found)

I am currently trying to promote my 2012 Server to a Domain Controller but when I am at the first step in the setup I get the Error Message

(German, Original Message):

[Bereitstellungskonfiguration] Fehler bei der Bestimmung, ob der Zielserver bereits ein Domänencontroller ist: Der Typ [Microsoft.Directory.Services.Deployment.DeepTasks.DeepTasks] wurde nicht gefunden: Vergewissern Sie sich, dass die Assembly, die diesen Typ enthält, geladen ist.

(Translated to English):

Error while determining, if the Targetserver already is a Domain Controller: The Type [Microsoft.Directory.Services.Deployment.DeepTasks.DeepTasks] was not found: Make sure, that the assembly, that contains this type, is loaded.

Thus I can neither Configure the AD-DS nor deinstall them via Server Manager. Any Help how to fix that problem would be greatly appreciated.

"The server currently has IIS8, MySQL (both can not be removed), Sharepoint, TFS, and the Project 2012 Plugin. The Idea is to run an exchange server on this server and to run an exchange you need IIS, MsSQL and a DC."

That's definitely the wrongest possible approach to a domain controller, which should be this and nothing else. Infrastructure roles (DNS, DHCP) are ok, but web services (and especialy SharePoint and Exchange, which assume to have full control of a the server) are totally not ok.

I strongly advise against installing all of this on a DC.

If you really want to go down this route, you should first promote the (empty) server to DC, and only later install anythjing else. Installing lots of things on a server and then attempt a DC promotion is a recipe for disaster.