I liken the IFR stages of your training to bulding a skyscraper. It is so important to have your BASIC instrument scan down pat before trying to proceed with all the other things you mentioned. Don't take your eyes off the scan for more than a few seconds while doing tasks. A lot of people tend to do an approach brief or something and just stop looking at the instruments! Of course the aircraft goes into a spiral dive, or stall turn or something like that!
The basic scan is the foundation of the building, all the other calls, checks, clearoffs etc are the furnishings inside. If you have a good scan and are a bit slow with all the procedural type things at least you've got a foundation and with practise the other tasks will become easier to accomplish in the given time. If you are really good with procedures etc, but your scan is bad, the foundation is'nt there and it will come crashing down, flight after flight. anyway thats my 2 cents worth!