OTRS means we're dealing with those cases where the person is aware and kicking up a stink - we need to take action everywhere, but especially where attention isn't already being called to it - those complaining to OTRS are already better off than those not doing so.  The metric of "multiple vandalism" is very sensible, it is a measure of where someone has enough badwill in the world at large to attract problematic edits in the first place.  Your metric of "vandalism not reverted in X seconds" is also sensible, since it shows where problematic edits are likely to persist.  Both "where likely to be created" and "where likely to persist" are sensible points to focus on - I'm not sure how you can argue otherwise. D