However I have seen this recently it seems specific thralls are more proactive with shields rather than a complete full block holds, seems they target attacks with quick reactive blocks which seems effective when they actually connect with the incoming attacks.
However the same cannot be said for heavy axe blocks, this seems to actually have horrendous timing between attacks and blocks as it cannot decide to fully commit to a attack or stop midway and block. Would rather him use a Axe with reactive blocks but it seems to be a full hold for my experiences with the thralls. Another thing is the best blockers seem to be based on in game race and class, archers seem to block the best, Cimmarian, Nordheimer, seem to preform the best in my experience.