What governs the success of your shield block or your dodge is first the stat comparisons, and then modifiers to the roll.
If you have a level 1 (novice) dodger and shield user, the night troll who has level 6 (talented) biter is going to bite you. A 5 level stat gulf is just too big.
Modifiers to the roll are whether you're at
Focused or
Focused!, if you're at 1.000 walking speed or at under 0.300 walking speed, if they can attack you from the side or back, and if you have chosen to manually defend (search: "in which case that really improves your rolls, for a parry, and *decreases* your dodge and block rolls") ->
(you get a boost to your choice, but a there's nerf to the others), stat penalties from being
drowsy/
stunned/
nauseous, etc.
For defense (dodge, shield block, parry with weapon vs. weapon) against 1 opponent, each will only trigger once per turn.
Now with more than 1 opponent, both block or parry will be able to respond once per turn,
but passive AI dodge can respond as many times as needed (best going
full passive defense as the rolls are flat across since there was no manual choice).
When you fight animals, they attack with "natural attacks" which can only be blocked or dodged. They don't have skill levels, so just having novice level 1 skill should be enough for the stat comparisons.
(Search: "If you're doing a lot of parrying") ->
What governs whether you dodge, block or parry is what stat is highest, along with how you have your combat preferences set. If your Dodge Preference is set to Stand Ground, your character will remain in the same tile. If set to Move Around, you'll dodge away, out of that tile onto another tile. So even if your character is set to Move Around, when you have a higher shield user, it's more likely that you'll not just block more often, but often stay in the same tile, countermanding your setting.