Lets take a look to the current state on healers after orkham patch and corruption system. Be honest, only 2 healer class combination is alive, you know which ones. Yes, i agree with lutine's post above, earlier, crossbow gave not bad advantage over others, but i could make up for it with something else in my class(of course not all classes were suitable for it). Now all another healers is trash(very sorry), because buff 800k atk better, than my ~600k, but i have +5% all attributes buff for raid, although there are many worthy healers. If dont touch the crossbow, then i see such solutions:
1) Boost another buffs (for example you give ~700k atk + something elite skill which give for example 6% atk more, i wrote about change priest/rogue, i think not bad solution. And in druid/bard's crocodile looks very good xd)
2) Buff formula needs in correction, need add more components(for example passive skills on wisdom), at the same time weakening the influence of unbuffed wisdom.
Until something is done about it, i not see reason write something about changes in healers, because we have absolute answer: priest/scout and druid/scout.