I havent got my copy yet so ive havent played Mu-12 yet. But what I know vs rushdown is to keep distance with 5C, and lasers if you are at long range, you can also use Tsungui(i think its called, her shield move) to push them away, but do not spam it so it becomes predictable. 2C vs jump-ins stops most of their moves. The most important thing is to keep your distance and poke, since Ragna or (insert rush-down character here) can be really scary up-close.
Check dis shid out me bredda.
Mu vs Tager Matchup
http://www.dustloop.com/forums/showthread.php?9186-Mu-12-vs-Tager