Eyeing me some Rocksmith DLC myself. They only go on sale once or twice a year (Summer and Winter Sales,) so I have to grab them when I can. Particularly Rush's Tom Sawyer and maybe Green Day or The Who.
Also, some advice for Steam sales: don't buy a game unless its a Daily Deal, Flash Sale, or Community Choice until the next to last day (the 29th this time.) It won't go higher before then, but it might go lower. The exceptions to this are games that are already discounted so much that they won't go lower. (Generally, this means 80% or more off.)