Honestly though mate, that defeat at Watford, and his ridiculous selection in the following game starting Gbamin in a 2 man midfield was where a lot of people lost faith. I seem to recall him bringing on Iwobi for Gordon who was our best player that day, in that Watford game. Sometimes you can just see a manager hasn't got a clue, and that was a big eye opener.
For me he should have gone after the derby, when he made ridiculous comments after the match, went with a 2 man midfield to accomodate Rondon, and kept playing Keane/Coleman.
In general I agree with you, we do call for sackings too quickly, but outside of Allardyce, can we honestly say any of Benitez, Silva and Koeman really had any ideas left when they went? All 3 could, and possibly would have taken us down.