Well, in that case. Good choice on who to give Shadowmourne. But don't feel bad, the first member we gave Shadowmourne was a warrior who sold his account the same day he completed it. We then merged with another guild whose first Shadowmourne wielder has gone afk until Cataclysm. Just thought I'd share.
Anyway, to the point. Arcane magi should never be brought to a raid if there's an availible ret paladin. Same goes for elemental shamans if there's a warlock and moonkin.