I have the same device and had the same problem.
Instead of using TWRP or the ordinary CWM, @Ripshock
suggested to me Phils CWM v2, here
, and with absolutely one try, I had my RocketTab 3.1 up and running.
Just remember to always perform a backup with each recovery you experiment with. From personal experience TWRP, CWM and Phil's CWM v2, each backup differently, therefore, they only restore the backup they made (so i assume). But so far, my Tab works like a charm.
E: it sits at the Galaxy Tab screen because there is no OS installed once that system mount error occurs. Restore the stock backup and flash Phils CWM v2 with Odin.