I am now thinking it is because of the raid set up.
It is. Your data is striped across two disks so no one disk contains any usable information. Both disks are required to access your data.
If I purchased a 2 bay external enclosure that supports Raid, would I have better luck in accessing the drives ?
There's no guarantee that it will work. There's no industry standard for RAID and different chipset providers implement RAID slightly differently. If however your RAID is a Windows software version then it'll probably work.
.............and have opted for a mirror formation.
That's an odd choice for a home user. Some folks think it's a backup but it's not. RAID 1 is normally used in corporate web and file servers so if one drive fails there's no disruption to the business operations. RAID 1 makes read operations faster so may be that's why you've chosen it.
Sorry I didn't give you the good news you were hoping for.