I agree with setting xbows in ground only for farming. If someone wants to use drags or looinion attack to get me, go for it. It rarely happens. I almost never get hogged either, but again if someone wants to use that huge army to get at my resources, they can. My main objective in a farming base is to defend my DE and half my storages vs l6/7 giant and barch attacks. Those are 95% of the attacks that you'll see.
I suggested witches to wannabe, but he isn't in a warring clan. Those are of no use to him outside of war.
Personally, i prefer upgrading Wiz Towers prior to mortars. The dark purple is a huge deterrent, and they can still 1 shot l5 archers and fire much faster. I tend to find mortars too slow. By the time they hit the ground, any strong barch attack will have moved and the mortar whiffing. I set mortars back to be in range of the second level where they troops bunch up/funnel at the 2nd level walls.
Upgrading the AD early is more for war i guess. But it's still good for healer/giant attacks.
Spell factory i think should be one of the first things to upgrade. Not only for war, but for farming. It allows you to raid longer without having to wait for spells. I typically hold 4 heal spells with my giant/barch attacks. usually using 1 heal per raid if needed.
I've been TH9 for about 2 months, and ever since my xbows maxed, i almost never get hit for DE (sans the lightning zaps when i held 120k) and rarely do i get 50%'d. Maybe 1 in 100. Most just TH snipe.
Biggest deterrents with a farming base IMO are black xbows, and dark purple wiz towers.
I agree with everything you said right up to about masters II. Then it's just a bloodbath. Up there, the would take my th as a security blanket and then it was an all out drive to the middle.