Opponent plays "dwarven battle cry". My dwarf rolls a 6 on his unreliable block and blocks it. Instead of drawing a card, he has thrown out an (admittedly crummy) ability. Might not be a bug, per se, but doesn't seem right in any case.
Hi, you are correct that this is counter intuitive and not a bug. In Card Hunter, your blocks will always play against enemy actions wether or not those actions are positive to you or negative. In the same vein, if one of your party attacks another party member, that attack will never trigger a block. I believe this was done for simplicity's sake (enemy actions bad, your actions good). You can use this to your advantage to draw out an opponent's blocks with Bungled Heal, Healing Pulse, etc.
