I just played a match with ... my memory fails me! Here's what happened: My warrior was 2 squares away from the said warrior with Defender's Block, my priest used Mass Frenzy which triggered Defender's Block - which resulted in my warrior not recieving Mass Frenzy. As description of the skill says: Block any within range of 3 of you or an ally. This was enemy warrior
Checked and there are some possible oddities with Defender's Block (and Cause Fumble). Will fix for Beta 1.22 or higher - let me know if seen again after that.
Just to add (although it's probably fixed as a result of the above), I was in a game with Nonesuch and my Wizard using Maze on my own warrior triggered his warrior's block. BATTLE LOG: Player=Jayce,Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Event=PlayAction,Action=Maze,Instigator=They're Short,Targets=Ibor the Mighty startTimer 0 1130 BATTLE LOG: Player=Jayce,Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Event=TriggerSucceed,Trigger=,TriggeringActor=Yorick,AffectedActors=Ibor the Mighty,TriggerType=Action,TriggerLocation=Hand StaticCardRenderer::checkTextArea Defender's Block Thumbnail Title is too wide. StaticCardRenderer::checkTextArea Defender's Block Thumbnail Title is too wide. BATTLE LOG: Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Msg=Ibor the Mighty, health = 21 (pi:1, gi:1, ai:0) blocks Maze BATTLE LOG: Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Msg=Maze was cancelled. StaticCardRenderer::checkTextArea Defender's Block Thumbnail Title is too wide. StaticCardRenderer::checkTextArea Defender's Block Thumbnail Title is too wide. StaticCardRenderer::checkTextArea Defender's Block Thumbnail Title is too wide. StaticCardRenderer::checkTextArea Defender's Block Thumbnail Title is too wide. stopTimer 0 1125 startTimer 1 1090 BATTLE LOG: Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Group=Yorick,Event=Discard,Card=Defender's Block BATTLE LOG: Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Msg=The active player is now Nonesuch BATTLE LOG: Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Msg=Nonesuch passed. BATTLE LOG: Scenario=MP Dungeon,Room=Jayce vs Nonesuch,RoomID=3318,Msg=The active player is now Jayce StaticCardRenderer::checkTextArea Defender's Block Thumbnail Title is too wide. Probably irrelevant after fix.