I consider a "totem" an item, and as such "casting" a spell for Shaman should be "throwing" a spell (literally) and therefore should NOT be silenced(able).
I find it appalling that Blizzard nerfed Shaman to the same magic as other similar classes.. to silence a shaman would only be possible if you killed them... We shaman can STILL throw something even when we can't utter an incantation to complete the spell during a silence, so in my opinion a silence would amount to putting a silencer on a gun in space.. you can't "hear" it anyway and thus negate the purpose for which it was intended.
A silence isn't possible for Shaman Totems specifically! we can be silenced but we can still "throw" a totem down....
If they want to disable totems you have to do it a different way