I cannot give you the details you seek, but can provide the following input/responses:

1) The server's IO is clearly not up to the task. RAID1 indicates just TWO spindles mirrored. The IO stalls and throughput you are seeing are just horrible for any production SQL Server work.

2) Adding RAM will NOT help with the disk WRITES (i.e. flushing tlog or dirty data pages to disk). You simply gotta have spindles (or SSDs) for that to happen at an acceptable rate (and an un-bottlenecked IO path). Period.

3) It is possible the load process underway is suboptimal and could be tuned. Could also be based off of the same disk(s) and possibly on the same system - all of which could be robbing the system of what little capacity it has from a CPU/RAM/IO perspective.

4) 64K NTFS cluster format size is preferred, but I cannot see it adding in nearly enough IO capacity to be more than a few percentage points improvement here. Now, if your volume(s) are not SECTOR ALIGNED, then I would definitely consider the strip-to-bare-metal required to get things put right. But I am virtually certain you will STILL not get what you want/need without better IOPs from your disk subsystem.