Hit rating has no effect on savage defence procs, but expertise does. Increasing hit rating just increases the number of normal hits, it does not increase the number of crits.
Basically to use tabletop mechanics, roll a d100, 0 to crit rating is a crit, crit rating to hit chance is a regular hit, hit chance to 100 is a miss. Increasing hit rating just means less misses not more crits.

I'm fairly certain hit has the same effect on SD as exp does, just less of it. WoW doesn't work on a single roll system, so your analogy is flawed at best. The major advantage of exp till soft cap is that it reduces parry AND dodge, as opposed to hit which just reducing misses. It also has a lower cap for us since we mostly only care about yellow attacks. The value of exp has nothing to do with hit not increasing SD uptime. Still hut overall is a lot less valuable than crit or mastery till you get extreme levels of crit.

Also, you have more mitigation from this setup, but you'll also end up taking slightly more damage due to having less avoidance. The nice trade off if extra dps, which is really nice in 5/10 man content. It also helps mitigate some of the streakiness by relying on SD procs rather than more dodges. AND it let's you go kitty for more damage if you spec right and gem/enchant agi primarily.

Also