You question is rather complex and you don't offer a lot of specifics, I am going to have to make some assumptions. First off, you dont need so many partitions. Yes, you can recover from a multitude of crashes if all your data is partitioned, but you have to be a Linux pro to do it. I only ever run with 4 partitions:
/ - the operating system files, usually fine with around 15GB
/home - everyones personal files, depends on the number of users, but with only one person I run with 15GB
/opt or /srv (depends if this is a workstation or server)- everything that I have added on top of the OS that isn't wholly dependent on system libs
swap - usually run with 2GB
The reason I run this way is so if something really goes south (bad) I can just format the / (root) directory and reinstall the OS, leaving homes and optional data alone. When it comes back up all I have to do is reinstall the apps that get installed in OS specific directories.
There is one issue I keep running into though. With only three drives there isn't a good RAID config that utilizes all three drives except RAID 5. You can do RAID 0 (mirror) but mirroring three drives is overkill. The only RAID config that will effectively use 3 drives is RAID 5, but unless you are doing hardware RAID, its going to impact overall performance unless tuned properly. You would get roughly 2TB of disk space with three drives in RAID 5, I would go that route and do some experiments with chunk size (I recommend 128KB). Your block size should be 4KB, unless you are running with a TON of small files. This will probably be the defaults in most modern distros. The nice thing about RAID 5 is you can lose any one drive and still recover, but be prepared, the rebuild on a software RAID 5 setup can be long and slow.
Here is how I would go after your system with the information you have given:
Hope this helps,
/ - 15GB
/opt - 400GB
swap - 2GB
SDB SDC SDD (md0):
/home - 2 TB (RAID level 5)