Oh, the default builds are almost always non-optimal. They've been a good starting point though, but as I've gotten more familiar with the shop I've started modifying what I get.

Off the top of my head, intensifying magazine isn't in Wraiths default build, but is great on her. Also Haze. It does mean you want to fire your entire mag continuosly because if you let up you lose the damage bonus.

Also, the top right corner has a button for browsing community builds, you can pick them and swap them on the fly, to try different builds out and see what other people are putting on different heroes.

Some even have "branching" structures where you buy different items depending on how the match is going and who is on the enemy team.