1.) no. blizz wants to homogenizise buffs. dk´s bring 20% haste, rets will bring it with cata, enh brings it
2.) no. the old wf totem was way to strong for certain classes while at the same time completely or almost completely useless for others ( feral druid and enh, rogue poisons )
3.) no. wf is THE melee shaman defining spell and it should be exclusive for them.
4.) no. it would make enh the by far best supporter and mandatory for every raid