https://cod.uberguy.net/html/power.html?power=circleofthorns.boss_succubus.blackclaw&at=boss_grunt
less need to do testing if you just look at CoD.
Blackclaw does -10% defense, but it is resistable.
I don’t feel like comparing CoD for every attack that does -def that CoT enemies have, but at level 50:
Magma Thorn Caster has 3 -def attacks
Succubus has 1
Master of Ruin has 3
If you want to see what the numbers those provide do, cross reference the HC wiki with CoD
https://homecoming.wiki/wiki/Circle_of_Thorns
alternately, you could turn off your defense toggle, pop enough oranges to be at the resist cap, and let CoT wail on you. Your DDR is all in SR passives, so you’ll see exactly how much -def each attack is doing and you’ll actually have a fair chance of getting hit.