This is true largely because it was an experience we learned from and have since made preparations in accordance with those events. Essentially, what happened with Cata's launch helped us to improve upon this.
I have responded to this before. What is pre-nerf content on the realm are things that are more basic and easy to implement, and won't cause problems for us going forward. It is not likely you will find pre-nerf raid content. There may be some, perhaps, but not likely to be much. The reason for this is because we're not soundly confident in the numbers and data we have access to - we tried a lot of it out on internal testing, and a lot of the material was extremely wonky (14k health defense capped tank getting 2-shotted wasn't fun, especially for me in the healer perspective). So we ended up going with data that we were more confident in using, in addition to not having to go back and re-adjust and "re-develop" content that we otherwise wouldn't need to. It's also kinda scary for us to comment on this for two reasons. The first reason being how mixed the answer really is for us. It's hard for us to provide a clear and concise answer to it. The second reason being that we do know there are a number of players who hinge their decisions based on a yes or a no to this question. (TLDR; The answer is mixed, TBH. Mostly no, to my knowledge anyway.)
You can expect some other things to be pre-2.1 nerf and pre-2.4 nerf however.
It is important to note that Kara, despite being such a cool place, is an entry-level raid. It being too difficult can be problematic, as it would roadblock many people from raiding. We don't necessarily want that.