A RAW recovery on a large files such as E01 files will always run a high risk of failure. Fragmentation is always going to issue.
If you are writing to a drive that is used for other purposes at the same time as the images was taken then I would agree. but writing to a partition that is used solely for images, as seems likely from the OP's post, then fragmentation becomes very much less of an issue.
FTR I have carved evidence files in this way on a few occasions over the years.
A raw recovery is a bit of a gamble, rebuilding the MBR, or in this case plugging the missing volume's boot sector into Encase is much faster, more reliable and should be tried first.
Raw recoveries are a last line of attack, to be used when you've got nothing else.
On top of this you've got to read the header of each of the images to identify its number in the set, does encase figure that out ?, (no I'm not testing it), if so how do /can you deal with two or more imaged devices in the same volume ?
But yes, if the drive was a clean(ed) hard drive with a fresh file system then the risk of fragmentation is reduced.
FWIW here's a thread where I discussed this some time ago.
http//forensicfocus.com/Forums/viewtopic/t=8000/postdays=0/postorder=asc/start=0/
Given the OP's apparent poor understanding of what is required (no offence meant) to recover the files and assuming that he is a forensic investigator then I would suggest that he makes time to try both techniques as TBH both are pretty basic, and again not wishing to offend, should be well within the competence of any forenisc investigator.
wrt to determining which files are from which image, if more than one. It is unlikely the images from different drives are interleaved unless either the images were taken at the same time or a smaller image has been deleted. But if the images were compressed (or different sizes - unlikely agreed) then starting and ending sector numbers from each image would do the job. I expect I could write a script/program to run though a set of images and name them appropriately with little effort.