preach it man. I've personally thought that a good singer is actually the hardest matchup for a shaman, period.
But I have only encountered a single *good* singer in all of d2, and he was a much better player than me
The real benefit against them is that most singers suck. But those very few *good* ones, well, they form the closest thing to a counter class a shaman has, since they rape them flat out if you do it right. The single grizzly hit you can land, the fissure pool you can camp in, won't do enough damage to intimidate him or fhr him with your cano, as they are the highest life (non shapeshift) build that there is, and once they warcry you once the duel is over. The good ones that use howl/leap just make it utterly impossible to win imo.
So consider that a weakness for shamans O_o