You only need the DAS (Domain Administration Server) for doing administrative tasks. It is not a crucial single point of failure during runtime. Of course you can arrange via other means for it to get re-started if it fails if you wish.
In the clustered environnment, the DAS is not used as a place to deploy and run your apps. Only the (in your case single) instance(s). When you deploy an app you deploy it to the cluster and the DAS will automatically deploy it to the instance, so in that sense there is no special complexity.
As for whether this is too complex for your needs or not, that is your judgment to make. I am only trying to help point out already available alternatives for you.
[Message sent by forum member 'lwhite' (lwhite)]
http://forums.java.net/jive/thread.jspa?messageID=345968