Legacy of War
The following abilities DO stack with each other.
Damage Reduction of the same type is stackable but only your highest DR that can apply will be applied – For example DR/- granted from Barbarian levels and from a magic item would stack but if a character has DR/- and DR/+ 4 only the highest would apply if it is able to. For example if a character has DR 3/- and 13/Bludgeoning and gets hit with a Great Club that will go through the DR 13/Bludgeoning, they will still be able to apply the DR 3/-.
The exception to this is with DR/+. These types of DRs will apply over top of each other. For example if a character has DR 5/ +2 and DR 5/ +6 and gets hit with a +4 weapon they will only have DR 5 but if they get hit with a +1 weapon they may stack both DRs and get DR 10.
Fast Healing from different sources is also stackable (up to DM discretion as some sources may override or negate other sources for story reasons.)