These things work because you have the right players for it. Its the reason why the wildcat works in Miami, they have the players for it. Its the reason why our defense works for us and wouldn't work for Miami, we have the players for it.
That tweener linebacker/safety has to be able to do two oddly hard to find things, cover and tackle. Quite a few linebackers can't cover a pass catching TE/RB. Plenty of safeties can't tackle.
We've been very fortunate that our safeties have been solid tacklers this season. Particularly surprised with Rolle coming in on run support.