It turned out to be the issue of Enrage:
http://larian.com/forums/ubbthreads.php?ubb=showflat&Number=619114#Post619114

As for backstab, some Warfare skills can do it, but it is not specified in their descriptions.

Battlestomp's damage is based on your attribute AND weapon. At least this is what I can read in the game and here http://divinityoriginalsin2.wiki.fextralife.com/Battle+Stomp

Last edited by Sotnik; 22/09/17 08:03 PM.