Hey guys,
From what I understand it's still not very clear what are the factors that will make Thrundarr give you the shield instead of Big Punch. Well I have been able to get it 3 times in a row with an L HE pally (latest steam version). It still may be a pure coincidence but here it goes.
I got the the last of Thrundarr's quests and went looking for the daemon but never found it. Went back to Thrundarr and got a quest to kill a Troll Chief so it's pretty clear that someone in the village killed the daemon. After completing the replacement quest I've been given the shield. On my other run I let the village kill the daemon and did the replacement quest, shield again. Same thing on the third run. I never had the axe on those run (I always try to be N when talking to the mystic).
Maybe a coincidence but it would be weird.