The OP would be well advised to discard the very obsolete Fowler. That book belongs in the dustbin. It is ancient.
The quoted text comes from Fowler, in the entry for "expect".
Everybody so far has got the wrong sense of "dead set". The phrase has 2 distinct uses
, the one shown is the SECOND of these:
1. Adjectival - firmly fixed, determined, not likely to change an opinion or plan.
(a person is dead set on or against something)
I am dead set against going on holiday to Greece this year; he is dead set on learning to fly.
2. Noun - a determined and targeted attack
(one makes a dead set against or at something) (This is rather obsolete, like the other phrase from Fowler the OP asked about)
Mr Wood and Mr Stafford made a dead set against the Commissioner of Customs
You wouldn't like it, I know, if the Bucks papers made a dead set against you & Father for being Jewish, & gave twisted motives for everything you did
One of these Hooligan crowds lately made a dead set against poor John
The Melbourne press made a dead set against me because, I am told on all sides, I am an American and Australia is frightfully jealous of Americans