The partitions are big enough when you don't get a 'No space left on device' error. There is no gain in making them bigger. Your partitions are *way* bigger than needed.
Maybe that is a problem. The bootloader is in flash, and it tries to load a kernel from sda10 and sda6. In this sequence. The kernel has a header which tells exactly how much bytes it is, but *maybe* the bootloader just loads the whole partition. In that case the difference between the Lacie partitions (8001 KiB) and your (71268 KiB) can be killing.
This disk is new? As I said, the 10th partition is probed first for a kernel. This partition is normally empty, but during a firmware upgrade the new kernel is written here. After a reboot this new kernel is booted. When the boot fails (corrupt kernel) you can reset the partition with a factory reset.
Anyway, the normal kernel header (uImage header) with magic number and checksum, should protect the box from trying to boot from garbage, but it doesn't hurt to clean up the partition, just in case:
dd if=/dev/zero of=/dev/sdb10
(This will exit with a 'No space left on device'. This is normal. /dev/zero can serve an infinite number of zero's, but /dev/sdb10 is finite)
On the multi-disk Lacie's there is a 'secret code' written in the unused space between MBR and 1st partition. (I *think* this is to show which disk is new, when a member of the raid array is replaced). The box won't boot if it can't find such a code.
AFAIK the NS2 doesn't use this, but it won't hurt to write the code:
echo "LaCieFirstBootLaCie" | dd bs=1 skip=1536 of=/dev/sdb
AFAIK the MBR is not used, except the (primary) partition table.
2TiB should be no problem. As long as fdisk doesn't complain, it's good. (Disks bigger than 2TiB cannot be partitioned using an 'Intel compatible' partition table. And I don't think the bootloader can handle something else.)
BTW, you are using the 1.0.2 partition dumps, aren't you? The also provided 1.2.6 paritions are stored in a different way (compressed partition versus compressed filesystem), and should be handled different.