The other interesting point is the word is used arbitrarily to describe teachers who
work for outfits that are disliked with little evidence that a given teacher is really
bad.

That's a good point!

However, in the case I am talking about, it would only be MY opinion as to whether I said he was a bad 'deecher' or not.

It's a TC, so no lesson-planning is required - just pick up the lesson and teach/deech it!

I am NES who has worked for many years alongside S.A people. I can hardly understand a word this guy says!

The students have to cope with British accents, Canadian accents and USA accents - that's hard enough - so when someone comes along whose Canadian, Australian and American colleagues can't understand, what hope do the kids have?