30-50 isn't really uncommon, after the release of AAA games...
that said, it didn't review well, and since if I remember correctly the studio was structured with about ~2 development teams of around 75 people each, one for thief (which probably isn't a success) and one for deus ex (which was a big sucess).
30-50 people from the thief team doesn't surprising or exactly undeserving. Considering that group had 5+ years to do a game that is decent... but quite shoddy compared to what the other group did.







