I seem to remember having the felsteel crafted set when I first started MTing Karazhan. I eventually filled that in with Heroic gear, then replaced it all with tier4/Karazhan gear. Heroic badge gear would be an interesting addition too.
The Prince is quite often a fight based on luck more than skill. A lucky sampling of infernal drops can make a poor group succeed, while an unlucky one can make the best group wipe. Once you gear up a bit, you'll at least hit the 50% success ratio.