I'm not sure if this is how it's supposed to be, but it seems odd to me.
I was spectating a game and saw a lerk firing spikes at a turret standing beyond a marine res tower. The spikes were flying "through" the res tower (hitting the model, but not at the "core part" that is solid) and hitting the turret. The odd thing is that the res tower took damage (and quite a lot of damage, it seemed), while the turret stood unscratched.
I've also noted as marine that sometimes spikes do no damage at all and sometimes they just rip me apart. The same goes for OC spit, btw. A couple of times I've been firing away at a bunch of OCs with a HMG, unloaded a full clip and taken no damage at all even when I see that I've been hit.
Anyways, sorry if this has been brought up already, just wanted to know if this is how it's supposed to be.