Not a bad lead. If I matched up against my lead, LO Mamoswine, Taunt would nix my SR if you lead with that, but you would not OHKO it with Heat Wave (69.06% - 81.77% to 4 HP Mamo). EDIT: no OHKO w/o a crit
Regardless you would get OHKO'd with the return attacked Ice Shard and I'm left with...