I don’t know if this is intended, but I find it quite strange that you lose stacks of “Feel no Pain” if you block or use the special with the slab shield. In think the patch notes stated, that you lose stacks by getting any form of damage (health or toughness). This is not the case if you block/special, perhaps stamina-loss would count as damage, too, but than you wouldn’t lose stacks, using the special.
I could understand that you would not regenerate stacks while blocking or specialing, but actively losing seems odd to me, espacially with the shield…
Pretty sure this has been acknowledged as a bug, but I can’t find the source.
Bug acknowledged here