If you are going to play solely hardstyle, then you need to be damn good. It's as simple as that because the only slots you will get in a club will be from 12 onwards, and depending on how late your club licensing in your city is, it might not give you much of a chance.
Personally I absolutely hate hearing music too hard at least until after 11 o'clock. It kills the night because there is nowhere you can go after that but back down, and it's too early for that. Many times I have turned up to a gig to play the main slot and arrived at 10 to hear a DJ playing exactly what I would which means i've then got to tone it down a bit, which might affect the people in the club's enjoyment. The only thing you can really aim for if you are up and coming is the later slots, the graveyard shifts if you like. No-one minds you banging it out then.
I can totally undestand where promoters come from, because it takes a very well skilled DJ to be able to create highs and lows with just hardstyle or any kind of hard music. It's a subtle thing that many people don't even see, but you can be assured that all of the DJ's mentioned who stand out are more than aware of it. Promoters listen to CDs, so perhaps if you're not getting booked, you simply may just need to get back to the bedroom practising.
It's easy to blame club politics after all (though they do exist) but sometimes you need to be fairer to the clubs. Most clubs don't cater for hard dance, not because they are scared of the druggy reputation - it's more that drug users don't buy drinks, and that's where most clubs gain their profit. I don't like the fact that people who bring entourages get bookings easier, but it makes sense for the promoters. The only thing to do there is get more friends!