if an opponent is healed by, say, Greater heal that only adds one power to a unit attached with blessing of Isha even if greater heal healed more than one damage right?

First, I think you mean Isha's Gaze, right? Second, yes, I think it is 1P per Unit healed, regardless of the amount of HP healed.

oops, yeah. I meant ishas gaze my bad.

IS this 1p per unit healed or just 1p if at least one unit was healed?