I also have quite a concern over the use of diacetyl/AP in e-liquids. As a result I've taken measures that I feel minimize the risk greatly.
For one, I've started cutting the pre-mixed juices that I enjoy (and I know they have quite a bit of diacetyl/AP in them) with straight VG. I've found that you can actually cut most pre-mixed juices with a LOT of VG/PG before flavoring begins to become noticeably muted. In an RDA with no reduced airflow, I'm not "flavor-chasing" by any means anyway, so no major flavor loss surprisingly.
Not only that, I've begun DIY-ing with extremely small amounts of flavorings that I'm very confident have no diacetyl/AP in them.
In reality, the diacetyl/AP thing is scary just because of the "we don't know what happens" factor. We're the guinea pigs. All evidence seems to say we'll be fine, but there's still that remote possibility that we're inhaling harmful chemicals. A big part of the question is "how harmful?" As long as it's less than cigarettes, I'm fine to continue vaping. The real disconcerting thing is "only time will tell." Even if people are getting sick because of vaping, it'll take them years to link the two.
There are a lot of discussions all over the forum, some of which I've started, many of which I've participated in. The underlying factor is that you need to make the best decision you can in favor of your health. I'd suggest steering clear of any juices which have claimed to be diacetyl-free but are later proven to be chock full of diacetyl (Cuttwood comes to mind.. Suicide Bunny.. A few other juice companies).