Why such a large gap between some heals?

[Snowaeth]

Here's how you can get the biggest gap between heals and the gap is seriously big then.

Eos buff = 20% heal/magic dmg increase.
Convalescence = Tank buff which Warriors can have too 20% increase in heals done to the tank.
Thrill of Battle = 20% more heals done to warrior
Defiance = 20% more heals done to warrior
Mantra = 20% more healing done to party members near the monk

If you manage to combine all this together you can see an increase of more than double efficiency.
Then if you manage to land a critical hit it's just silly