It should also be said that those in favor of using HS as an active cool down might want to be careful not to come across as someone who undervalues passive mitigation.
On one hand HS is on a cooldown but doesn't really reduce the (usually unblockable) damage bursts themselves,
The end result between these two approaches may be very similar anyway, but we should probably achieve some form of general consensus and make our recommendation in the OP.
I completely understand your concern, regarding undervaluing passive mitigatin, and believe me it made me wince at first when I saw this version of the new HS. However, I think you really have to ask yourself a question. Is the average auto attack going to cause too much damage, at least in respect to other classes? I don't think this gives warriors an advantage over us regarding damage, as they don't usually have a guaranteed block chance (yet) if they don't have shield block/some sort of a proc active. That 30% damage reduction is guaranteed for us, at least as of yet. As for druids and DKs, I know how they work in general but only have a surface understanding of their mechanics, since I have not played them, but it doesn't seem to me that their absorb shields will be way ahead of mitigation, especially the druid variety since it is based on the RNG of crit. Even if we never use the active HS, I don't think it would ruin us in respect to other tanking classes.
Now that is an extreme conclusion and I'm not saying to not use HS. I just think that 30% guaranteed physical damage reduction from auto attack is still great. If we need 10% more passive damage reduction on a fight it is probably because there is an issue other than tanking. With that said, if there IS an issue (especially when learning an encounter), then they usually occur spontaneously and sporadically over the course of the fight. If the heals have to spend a little extra time healing dps the new HS suddenly becomes much more valuable than the old HS. If the heals have to move or are incapacity, then again the new HS is more valuable.
I'm not trying to say there aren't any drawbacks to the New HS, but rather, I think the short cooldown makes it MORE meaningful to press rather than less because it can be an ability that you go to when there are little problems and save the actual damage reduction cooldowns for burst. As it stands right now, you have to use DP/AD/GoAK any time there is a problem or burst (which may be enough already), but now we can pretty much always use HS for the "little stuff" (or a little extra damage reduction during burst to guard from auto attacks) and still have our more major cooldowns ready. We often think that the only time a tank dies is during burst damage, but that isn't *entirely* true. I think we can also add that a great deal of tank deaths have been caused by too much damage on the whole raid. Often times, the healers will pick the tank over the dps, but then dps becomes slower and as the fight progresses, then the tank becomes more and more likely to die. The job of a tank is to keep the dps alive, and if the healers have to choose the tank over the dps in a certain situation, then the tank is essentially failing in that job.
Now at this point, the old HS may be better in some circumstances, in other circumstances the new HS. Perhaps in some circumstances the 10% extra block amount never causes healers to choose, in other circumstances the tank can activate HS to give 20% block amount allowing the healers to focus on raid healing. The only difference is that the power is more in the hands of the player, and honestly, I think that is what the problem is with the new HS. I like the mechanics of the new HS, but I honestly think that the key bindings are becoming a little too overbearing. (that may be because I already have stoneform and mirror of broken images macro key bound as well, not all paladins actually have those)
I guess this is just a long way of saying that we really can't say which is better until we actually see which version will save us more times (which is basically unfalsifiable anyways). In regarding to coming to a consensus of how exactly to use HS in the op, I think we do have a consensus, though not specifically for HS. I think it says something about you only get as much mileage out of CDs as you use them and they are best saved for periods of heavy burst or raid damage, but if you aren't going to use the CDs in that way it is best to macro them into your rotation. Maybe you want it to be a little more explicit regarding HS?