Likewise if you think having an achievement, an item, no soldiery means someone by default capable of actually clearing something then your ignorant of the flaws within that stance. The people who think soldiery is a good way to judge the competence and ability of another player are the incredibly naive. I have had people with achievements and item links wiping the group almost as much as those with soldiery, yes you will get the new players who do not bother learning the fight one way or another and yes they may cause wipes from time to time but you also get a vast amount of people with clears who will cause wipes constantly.
The way you get people who know the fight is not by saying no soldiery, it is by saying know the fight and that is all you need to say...it includes watched videos, read guides or experienced in game and deters most non-experienced and non-research players form signing up. Someone who has done the research is just as likely to be as competent as someone which has a clear or achievement to their name and merely saying only those who know the fight is enough in most cases to get only those people.
The flaws in your no soldiery stance are not limited potentially a person carried by the competence of others as to why some get that achievement or that item, it is not limited to the competence of others that might have been paid to get that potentially incompetent person the achievement or item...the fact remains on top of those having potentially occurred it could also be the case that achievement or item listing person might not have even done the place in week/months or maybe only done it once and may have forgotten the mechanics compared to the new player actually reading the guides and watching the videos many times on that very same day and as such the new player actually knows the mechanics better than the person with the achievement/item since it is fresh still in their memory.
I do a lot of EX farm PF's of late for mounts and such and a lot of the wipes are from the people who claimed to have cleared it before, what a nice and wise person does is list as a requirement of knowing the basics but what a selfish, naive and lazy person does is exclude people based on soldiery. Knowing the basics includes having done it before and/or having read the guides and/or having watched the videos explaining the mechanics and phases of the fight including potentially if good guide or video explaining your job within it.
There is no 'good' reason to exclude someone based on soldiery, you are just as capable of voting out someone who is new and never bothered to read the guides or watch the videos and as such leads to deaths as you are from voting out the people who claim to have cleared but keep on failing still. Fact is your not excluding people based on the actual ability to do something, you are excluding them based on your own ignorance while using a highly flawed baseline for that exclusion.
In my experience just as many achievement/item/cleared players tend to get voted out as new ones within the party because of wipes/deaths...which is based on PF's which lists just knowing the basics through guide/video or having done it before and that better gauges the difference between new players who did the research vs players with achievement/items since new players who never did the research don't end up joining often even without the 'soldiery=kick' crap. Just saying know the basics or know the fight is ample restriction if want to restrict it in a less selfish and less ignorant way compared to no soldiery allowed.
They should remove the soldiery notification at the start of the runs so people like you will stop abusing it to exclude people who are more often than not quite capable of clearing the content as long as you ask people to learn the fight or know the basics from either experience, guides or videos within the PF listing instead of your no soldiery crap. The notification should be removed and instead just tell people at the end that they got a bonus because a new person was present.