While these are technically "combat style" feats, they add super little defense value relative to other sources of Physical Resistance Rating when used with a large shield.
comparing:
1 x feat: +5PRR ( only 7 available by standard )
to:
1 x past life feat (stacking many times): +3PRR
1 x filigree: +3PRR
1 x ap: commonly* +3PRR
1 x accessory mythic II bonus: +3PRR
1 x shield and armor mythic II bonus: +4PRR
1 x reaper defense bonus: +3PRR
Remnant Tome of PRR: up to +4 PRR. ( altho the price for the last 2 is not for everyone)
What i am trying to get at, is that the "build cost" relative to the PRR gained is relatively large, other sources of very available PRR are super close and abundant.
Say, a single high level sheltering item is 50+ PRR (commonly available), compare that to the 5PRR from a heroic feat called "Shield mastery" that needs an offhand slot. While set bonuses add circa +20PRR.
I cant see why a defensive cleric, fvs, or druid would want to take these feats who dont also melee, and if they melee they more likely to use twf or thf anyway.
As always thanks for your attention =)