Mosley has done well in coverage this year and in this game, plus he's the signal caller, so no problem there. Orr and McClellan have both been targets.
The Ravens have been playing a 1-down lineman pass rush package with just Jernigan (or Guy on Sunday) in a 3-point stance. The others are all standing (presumably to confuse on provide some coverage flexibility), but it seems McClellan is a fixture in that package. So the personnel on the field include:
--5 DBs
--Mosley and Orr
--Jernigan (primarily, it was Guy some in Q4 on Sunday)
--2 pass-rushing OLBs from among Suggs, Judon, and Smith
--McClellan
On Sunday, for example, McClellan played 27 of the 34 snaps in Q4.
If Levine took the spot of Orr in this package, he would (and did during Mosley's absence) position himself similarly to either threaten the blitz or drop to coverage. He'd be a hell of a lot better in coverage and my contention is he's not much worse than Orr in terms of pass rush value, because both are looking for a free run to get home, not to beat a blocker. Levine's short area coverage skills were on full display during the preseason, and the Ravens always did well with the dime prior to Pees' arrival.
As an alternative, if Pees wants to keep Orr on the field, he can remove McClellan and have Orr take Albert's roll in the dime package.