In my poorly-supported opinion, Anthony Rabasa is a bigtime athlete who has gotten mired in two dilemmas: 1). a preferred position [hand on ground and violent rush] which has been occupied by several NFL-quality players [Tuitt, KLM, Day... even non-NFL studs like Hounshell when healthy] and 2). is not quite fitted for the linebacking corps [somewhat a la Ishaq] in that he hasn't acquired linebacking instincts.
Still, Rabasa is a very good athlete, and if we had not been so loaded at some of these positions so that he could get reps, I believe that he could have been/ will be{?} productive. I saw a play in the Spring Game where his pass-defense-in-space instincts looked very good. This is one of those things which happens so often at a school like Notre Dame which can recruit so many elite and near-elite potential starters.
Biggest mystery to me is that no more of them transfer. Some of that must relate to the ND degree they'll be getting.