Cabin crew and maintenance don't seem unreasonable considering the scale of the Shannon operation. I can't really comment on the cargo figure.
Ground ops does seem high, but that is presumably where the bulk of the cuts will be located. With only three flights a day to be handled, third party handling would definitely make sense. I'd imagine that after Heathrow is withdrawn, the number of Aer Lingus pax going through Shannon will be lower than airports like Schiphol and Birmingham where third parties are used.
The fact EI are only laying off a portion of the staff rather than getting rid of ground ops (either through sale or closing down) while signing a third party handling contract suggests to me that operations are being wound down .