I know the DP causes damage and kind of remember the enforcer and razorjack also. I didn't notice pupae, slith or Skaarj being damaged by walking over/through blobs.
And as concerns AI, why do they only go after the player, it seems more in line with other actors that if they are damaged by these, they should act with a vengeance.
I can comfirm that walking through blobs doesn't always cause damage. They have to be engaged on you, and the damage causing isn't by touching them...but by their melee attack. Pawns that walk over a quiet blob won't get hurt, player included. I haven't actually seen a blob attack a non-player pawn, but Unreal has a very general "you hurt me I'll hurt you back" setup for enemies. Although, since the blobs themselves are very underdeveloped...
Another strange thing with the blobs is that after some time they stop following the player (so do some other actors once out of view, but at least when they see the player again they remember who to attack).
If you outrun them...if you cross through a teleporter, ride a lift...it sort of breaks their A.I. It's like they don't have very good scripting for losing sight of the player once engaged for combat (probably explains their confined use in Unreal and RTNP). This has been an issue with Dead Cell too. One I'm trying to circumvent through various...strategies
And yes, the spot to hurt them is difficult to hit, one or two is still feasible but when there are 4 or 5 together it seems the already dead blobs block the "missiles" until these blobs disappear.
Unreal isn't very good with precision hitting. That's the real problem. At least in regards to collision cylinders for actors. And the blob's hitting collision zone is basically 10 units. That's like trying to shoot a bunch of Acoustic Dampeners as they chase you in a group, or biterfish...with a non-splash weapon.