Well, on their own, they don't look so good to do all the heirlooms, but when you add the numbers together, it gives an advantage.
Guys, don't tell me that it does not, everyone knows it, right?
It's like the KERS of cRPG: Gives a slight boost only, but it can save your ass.
Well as an Archer heirlooms are still nice, you can focus on your bow and arrow, maybe a sidearm if you carry one with you.
But don't forget that if a player relies only on Heirloom Powers, then who controls who, the player the character, or is it the other way around?