Stuff stacks multiplicatively in most cases. Raging Strikes and Blood for Blood would end up with a total of 32% damage increase (1.2*1.1=1.32, or 32%).

In your second case, you'd have a total of 71.6% increased damage (1.3*1.2*1.1=1.716, or 71.6%).

Order doesn't matter, you can try switching the places of the numbers, but you'll get the same result every single time.

Bonus: Defensive cooldowns work the same way. With Grit active and using, say, Shadowskin, you end up with 36% damage reduction (0.8*0.8=0.64, or taking 64% of the full damage value), rather than 40% reduced damage!