Paladin Shields

[Donjo]

Because Block is checked before Parry, the total mitigation of the Shield Types depends on how much Parry you currently have, as each class of shield dilutes your parry rate by varying amounts.

A Buckler has the highest block rate and therefore the lowest Parry rate. Therefore, it's good for low Parry builds.

A Kite shield is the middle of the road. It is the best option if your Parry rate is roughly equal to the Block Rate.

A Tower Shield has the lowest block rate. Thus, it is also okay for high Parry builds.

The formula for block rate appears to be close enough to 0.1 * block rate + 10 to just use it for simple demonstrations. Let's calculate total physical mitigation rates at 2 different values of Parry.

1. 341(base)
Parry Rate: 10%

Diamond Shield: Block Rate 325 * 0.1 + 10 = 42.5% block rate.
57.5% of hits not blocked are parried at a 10% rate = 5.75% parry rate.
Total Mitigation Rate: 48.25%

High Allagan Kite Shield: Block Rate 211 * 0.1 + 10 = 31.1% block rate.
68.9% of hits not blocked are parried at a 10% rate = 6.89% parry rate.
Total Mitigation Rate: 37.99%

Noct Hoplon: Block Rate 129 * 0.1 + 10 = 22.9% block rate.
77.1% of hits not blocked are parried at a 10% rate = 7.71% parry rate.
Total Mitigation Rate: 30.61%

2. 600
Parry Rate: 29.43%

Diamond Shield: 42.5% block rate.
57.5% * 0.2943 = 16.92% parry rate.
Total Rate: 59.42%

HA Kite Shield: 31.1% block rate.
68.9% * 0.2943 = 20.27% parry rate.
Total Rate: 51.38%

Noct Hoplon: 22.9% block rate.
77.1% * 0.2943 = 22.69% parry rate.
Total Rate: 45.59%

Important things to consider:
1. Bucklers reduce damage less than Parry does when it procs a block. Therefore, you'd actually want to Parry more often for maximum mitigation.
2. Kite Shields reduce more damage than Parry does when it procs a block, but not by too much. Therefore, it doesn't really matter which one it hits.
3. Tower Shields reduce far more damage than Parry does when it procs a block, but at a low rate. Thus, a high Parry rate helps to counterbalance it.

Without running simulations and whatnot, I think that Kite Shields are the best all around shield if your Parry is high. If you're running low Parry and just want to block things more often, go for a Buckler because a low Parry rate can't be hurt much by the dilution and some mitigation is better than none. Towers are in an odd place. They're absurdly powerful under Bulwark and they allow Parry to do the most work out of all of the other Shield Types. I'm not sure if it would be better than Kite or Buckler in most situations; it might be a highly situational choice.