Raid is toast. I dont care WHAT raid you are running, none of them can withstand a loss of 50% of the drives.
Really? I used to do that as a routine acceptance test for clusters. The only times it failed for real was when we'd screwed up something.
For that to work, you have to rigorously separate RAID mirrors into their own trays so that a whole tray failure (or cable, as you said) only takes one mirror down. For something like 10, 50, 60 you just make sure all of one side is on one array and all of the other on another (or if you have more than 2 arrays, that you separate them out into pairs with one used for one side and one for another).
Physical separation helps as well, so that you don't accidentally unplug A while starting servicing on B. That exact scenario is one of the canonical HA oopses.