What exactly are you trying to probe?
A full surface, or a perimeter?

Probe-it's strength is perimeter probing, be that probing the complete perimeter, or finding an edge/centre.
The surface probing is more suited to things like PCB machining, where you probe the material surface to apply a transformation to the g-code so you get constant depth machining.

If you're wanting to do surface probing, you'd be better of looking at Art's Digitise Wizard plugin that uses a bed of nails approach to probe the entire surface. It's not the fastest method though.