Shadowform, as everyone knows, is the bread and butter for shadowpriests.
It gives us +shadowdamage, -15% physical, increases our DoTs damage by our crit chance and reduces our threat (Next patch: -15% all damage and dots crit). But the downside is that we cannot use holy spells, thus making us unable to heal ourselves or others.
It also costs 32% base mana (1161 mana for an UD with Shadow Focus)
Now look at Druids, the have 2 shapeshifts that rely on mana.
Moonkin and Tree of Life.
Moonkin form increases armor from items by 360%, all raid members within 45 yards get 5% spell critical strike chance, they have a chance when they crit with a spell to regenerate 2% of their mana instantly and when they shapeshift they remove all Polymorph and Movement Impairing effects on themselves.
While Moonkin form is active you cannot cast restoration spells, except for Remove Curse.
It costs 22% base mana, 10% lower than Shadowform(for those who can't do the math)
Tree of Life increases healing received by 6% for all raid members within 45 yards, reduces 20% mana cost of all healing over time spells.
Also removes all Polymorph and Movement Impairing effects.
Costs 28% base mana and cannot cast balance spells excluding couple of spells.
(Next patch: Tree of Life gets 260% more armor from items, base mana cost reduced to 13% but no longer reduces the mana cost for HoT spells)
Tree of Life: 28% (13%)
So now, I'll let you decide, is this fair?