Well, here it is. Dell's idea of RAID10 is creating two or more mirrored sets, and then concatenating them. What this "concatenation" means that it spans across those mirrored sets, as opposed to striping them (which is what RAID10 is), so it's not really a RAID10. You don't get the performance benefits of RAID10 from it, as it accesses the spanned volumes one at a time, as opposed to accessing them all at the same time in a proper striping set.
However, it was possible (although not very intuitive) to create proper RAID10 is you used HBA's BIOS, as opposed to Dell Array Manager GUI, in Perc3/DC. I'm not sure if PERC4/DC allows to do it in a BIOS as well. If anyone has PERC4/DC and 4 spare drives, I'd appreciate the feedback.
The way you did this in PERC3/DC was to create 2 or more mirrored sets first, and then choose those volumes to create a RAID0 volume.