If the jet behind is too close, I will ask to be re-positioned in the pattern. Never will I knowingly descend at, or below the glide path of the jet ahead. He was very fortunate to have survived with minor injuries. I prefer not to tempt fate and end up in the same attitude as he. Thus, when flying IFR, and accepting a visual approach clearance, the ball's in your court.
Controllers are no longer responsible for separation and wake turbulence avoidance.
If you are uncertain as to where or at what altitude leading traffic is, decline the visual, and shift responsibility back with the controller. In a recent article, I discussed assumption of the risk. Do so, and be prepared to pay the consequences.