Damn yeah, that atty without the collar sits bad, I wouldn't like mine that way, looks like it could break. On the other hand, an RDA is not very big or clumsy so probably not altogether a bad choice to put on there, compared to something with a tank which has a lot more weight above the thread. If that collar/ring fits your device you would do well to get if only to support what you have sitting on top, even it's not the prettiest.
Why can't they get these things right ? I have the itaste mvp & almost none of my attys will make contact with the centre pin. I have to use an ego thread To 510 adapter which makes the whole thing way clumsy. I'll get round to remedying it some time. I prefer my mech !
If all else fails, get a nemesis, a pair of decent 18650 batts & a good charger. End of issue.