[hider=My Hider]
Krootboss: http://puu.sh/oQsXj/575d114c42.png
2 hits
1d10+9 damage each
http://puu.sh/oQt08/953e887998.png
14 damage and 15 damage
Due to damage soaking and armour  = O damage

Kroot fighting Bacara: http://puu.sh/oQt7e/37b13ebfc3.png
No hits

Kroot fighting Dominous: http://puu.sh/oQt8U/9ebb44a8cb.png
Hit
1d10+5 damage:
http://puu.sh/oQtad/4cb16d8f63.png
15, and that would prompt a crit, but astartes are immune to low-level crits I believe.
I will say that you take a single point of damage instead of a crit in this case, as the damage would otherwise not do anything...

Tau firing line: 3 tau = 12 shots needing 20 or lower to hit
http://puu.sh/oQu71/d15d706223.png
5 hits at 2d10+2
http://puu.sh/oQu9k/b8da5a47dc.png
16 - Librarian
15 - Librarian
19 - Librarian
12 - Fellwalker
6 - Fellwalker
Librarian = 18 damage soak = 1 damage taken
Fellwalker = 18 damage soak = 0 damage taken
[/hider]