Why is healing so random?

[Firangi]

Sometimes I heal myself for 99 hp, sometimes I crit for 130, and then sometimes I heal (without a crit) for over 200.

...I feel like I'm missing something here. Does anybody know what?

 

[Kingu2]

bleed halfs the amount healing received. buffs that increase spellpower and debuffs that lower it can also effect healing from spells.

 

[Firangi]

bleed halfs the amount healing received. buffs that increase spellpower and debuffs that lower it can also effect healing from spells.

Thank you.