This is wrong, very wrong. Whether a gank succeeds or not should be based solely on how well each of the involved parties plays the game, not chance based (other than the chance based way in which weapons work already).
Suicide ganking is just like normal PvP, with the only difference that the ganker has a limited amount of time available to succeed before being killed himself. Why should the ganker artificially fail at least 50% of the times regardless of how well he does it or how badly the victim fits and flies his ship, and still face 100% guaranteed death himself? Why should suicide ganking in high sec, but not (non-suicide) ganking in low sec, have such an arbitrary failure rate? Makes no sense.