I personally dont feel that the healing amount to mana cost ratio is the problem, its simply the flat cost of mana. Our vivfy should not be as strong a Holy Priest Stronger heal was last x pac.
I think that for this, they could bring back the original mana tea where it restored mana instead of spells costing less mana for 10 secs every 2 mins.
My suggestion is: Mana tea restores 4000 mana. Contains 2 charges. Recharge time is 30 secs. (thats 8% of base mana back every 30 secs)
Vivify mana costs is reduced to 3.5% Base mana cost. (currently 4.1%)
Enveloping Mist is now instant but has a 5 sec CD. (much like Shaman Riptide) Mana cost reduced to 5% base mana cost. (currently 6%)
Essence Font mana cost reduced to 6% base mana cost. (currently 7.1%)