Slumber is not really a combat heal and has its own set of issues as a Slow duration heal, meaning for high DPS mobs its basically worthless. Mend wounds I was comparing to Complete Heal, and Words of Completition, Not to the lesser efficency heals of druids and clerics.
For mana per tic, Its not really fair to count Canni at full value. Yes, in theory a shaman could get around 160 mana per tic. But if you really play a shaman it doesnt work out to be that large. (if you are fighting alot of mobs every cast you make takes away from your potential mana regen, This is not the case for necro lich.)
What I was trying to say about a cleric with FT and a shaman with FT, was that as a healer, the efficency and use of Complete Heal (the amount healed per second), and the naturally low mana regen clerics have, makes FT 15 much more powerful on a cleric. No shaman will be healing a main tank on a raid simply because they have this Theoretical 160 FT.
"Do their spells suck THAT much?" When I was leveling up my druid, I was lucky enough to have Relic: Jayala's Boon cast on me. (back when it didnt have a level req.) You might think that 18 FT at level 30 would be completely unbalanced, but it didnt make you immortal. The spells themselves sucked in such a way that the casting time limited their use.
In the case with Mend Wounds and Slumber, go ahead and take a shaman to catacombs or cmal3 and try and be a main healer. It wont work no matter how much you punch canni4/5. Shaman and necro dots need a complete revision probably, so that shaman do not displace necros as damage over time masters. But, the 2 classes shouldnt be compared at all. Shamans need to be balanced against the other 2 priests. Is shaman mana regen displacing clerics? Is it displacing druids? In some situations I would say shaman DO displace druids, But not every. The harder the content you go for, the more Heals per second matter, and less how much FT you can conjure up.
""four times the mana regen of all classes""
The average CH in groups I am in is about 5k, for 455 mana. For a shaman to heal the same with Mend wounds (In combat not counting Slumber) -- It would take roughly 3.5 casts of Mend wounds (with no healing inc). 455 mana VS 1050 Mana.
(JB/KEI, is a enchanter enhancement. Having Kei not stack with Lich Hurts Enchanters, not Necros, same situation here. )
Shaman are too powerful at level 60 in a normal xp/equiped group. But not too powerful at 65 with a raid equiped group.