You generally get all the block (both value and chance) and strength naturally from gear, so while you 'gear' for it by grabbing upgrades, you don't need to gem or enchant for it, so you are right in that. You do seem to carry some common misconceptions around with you.
The guide you are talking about seems to be put together by someone who hasn't seriously tanked.
Block damage reduction is not negligible. On my pally I block most attacks, and I block for around 2k damage. On a 2stacked festergut, my block makes the difference between being able to take two hits and being able to take three hits. Even against a boss that hits for 30k per swing, my block reduces my damage taken by 6% or so, and that's huge.I would also rather improve the chance to totally avoid damage instead of improving the chance to mitigate a negligible amount of it.