Why not "C'est nul" ?
It has quite the same meaning.
"C'est nul" is more intense than "c'est dommage". You'd be angry saying C'est nul, while more sad saying C'est dommage.
or 'c'est trop mal'?????
No, you can't use a direct translation because it is a set phrase: "c'est dommage".
tant pis not accepted ?
The meaning of tant pis is more like "nevermind", or "it's not that important". C'est dommage matches more with "that's too bad", or "what a pity".
In that case, it is not a really good alternative. You don't usually include tant pis in a whole sentence. It is more a stand alone expression. And the meaning is a bit different. It means more or less there's nothing to do about it.