Yeah, when you have a high end shield it makes a HUGE difference. IIRC you get a bonus to your block skill equal to 3x your shield's AC. If you've got a 60+ ac shield, that cuts the number of hits you're taking enormously.
What I don't notice is that much of a difference with lower end shields, e.g. the starfall I result. I've looked around a bit and haven't been able to find much in the way of shields that fall between that one (obtainable at level 35 grouped, probably by 40 solo) and raid gear (e.g. za`yth). I wonder if it might be possible to put in a couple of high AC, low stat shields obtainable in the 50s or non-raid 60s that would provide that tanking boost for pallies and SKs. Something better than the 25ac of the Recovery II shield from CC and the like, but a significant step below the tier 2 and tier 3 drops that really start making a big difference.
For example, possibly something from a mob around the difficulty of mielC, eld's early castle, or deep CC, that you could get grouped in the high 50s or low 60s... maybe 40-45 AC and no stats or low stats... 10 or so stat points and maybe 25-30 hp and/or mana.
It seems like there should be some sort of stepping stone in there (there might be from adepts, but something a little more widely available) that doesn't require a huge leap from a level 35 rec shield to 65 raid gear.
Alternately, what about a deepmetal shield? (And if there is one already, wtf nasta! Send me one already!)