Yes i participated in the initial discussion of the system introduction. However as there were quite some serious life issues that happened i had to take a longer break.
Allthough even if it was introduced on the test server, i almost never use the test server. The only exception was when Har'Akir was introduced and i was shown around a bit of Har'akir on the test server.
(I fail to see though how mentioning that i am away or not adds anything to the discussion.)
With 18 ACP and raising the tower shield to offer 4 AC though, it would have been also the same in regards of final AC with shield parry. Since again you can have 2 AC from parry while wearing a chain shirt and using a tower shield and also varnish it. So it could again offer the AC of 10.
The bonus tower shield would offer though in this case would be for everyone else that is not using shield parry, and yet still uses a tower shield, since they would get 1 more AC with the change than previously.
I think what Hypatia means is:
For the greater two weapon defense you will need 19 dexterity and even for Agrippa 16.(And 14 int)
The points that you would be putting in dex for TWD, you can put instead of STR if you select Shield Parry.
And it goes the same for Agrippa.
The 19 dex for TWD is quite high. It would cost for most characters that are not elves about 5 ability points if they start with 16 dex. (I just assume a starting dex of 16, so they can have the GTWD on level 12)
This is 5 ability points you can place elsewhere. (not to mention the feats)
I've also seen many folks take up Parry feats to get the max bonus AC from Agrippa and TWD and later change it out. (I find this a bit cheesy but that is just my oppinion.) Which you likely are not that required using shield parry. (Simply because you can get the +3 AC from shield with an easily aquired strong varnish, with all the folks selling it! So effectively around 25 parry you can already get the +9 AC)
My char also have not yet had the luck to make adamantine shields, simply because my char had not aquired adamantine and likely will not for quite a while, even though he could likely easily smelt it, make weapons and shields out of it, and probably some lesser full plates too. That is my decision, since i am playing him with certain heavy restrictions.
But of what i've seen, i am guessing that adamantine shields give 5 soak beside the +1. (maybe at the cost of 2 dex no clue)
That is also something that adds an extra bonus to shield parry, since with TWD and Agrippa you wont have that.(Or you can just on item sets and so on.) And even if this is not the case, there are some very nice shields out there. That offer extra protection against certain spell damage types, or SR or well don't know since my knowledge of the loot table is likely outdated, having nearly nil knowledge of the higher level loot table and only seeing them in merchant inventories.(both PC and NPC)
I think many are misunderstanding what i mean though in the discussion. I find shield parry a very useful and good feat. I am merely pointing out that in comparision to Shield Parry the other AC bonus feats are weak. If you take into consideration especially the feat and possible item requirements. I would actually suggest that both Agrippa and GTWD should offer 4 AC instead of 3. The three feat requirement in my oppinion would balance out this way the requirement of shield being varnished/magic armoured.