It shouldnt be affected by battle fatigue but it should be for dampening. Guardian proccs without dampening --> u recieve 60% hp i guess and with ... let say 50% damp you recieve 30%hp. About the heal increasing part, its not affected by anything obv. Let say its 50% damp and you do a 50k serenity, with guardian ud heal around 80k i guess. Not sure if the procc amount i listed (or the healing reduce one) is 100% correct but yeah, thats how it is.