HP drain aura + Vigorous absorption
The reason why HP drain works a lot better in PvE is due how the monsters stat scale, they aren't as crazy as most players stats (also monsters usually are being constantly debuffed for bigger damage), take into account players will have higher physical and magic protection in compairson to monsters, and any sort of drain buff/debuff works best when you keep landing critical hits. On the other hand, if you fight a squishy player like me you will get your hp back
Blood Congeal & Petrify
Since Blood Congeal hits in a circle around the person casting it + you could zombie/boar-trans it off, I agree the AoE could be increased a little bit (maybe instead of 8m radius make it 10m?), about the cooldown though, Crusaders do have Killing Spree(CD reset, 3m CD time) which opens up possibilities to combo long CD skills
For the other point, Crusaders have Petrify 3 + Charge 2 , both of which have 10m of range and 80% chance for their debuffs to proc, and for upclose situations you have Unadulterated Strike, Blood Congeal + any transformation you
could use like lizard, nirenia etc, I guess having another immobilizing skill would be nice? hahaha, it would be interesting to have a different debuff that shares its cooldown with Blood Congeal so you trade having more range instead of immobilize + DoT idk lol
This is all in theory ofc, since any of those could miss, but that is how chance works haha