Is HRK trusted?

It was comparatively cheaper when it was in that G2A bundle. I haven't had any problems with HRK yet.

I only get giveaways from this site, but I read something that might help you:
http://whosgamingnow.net/discussion/2149/how-to-tell-if-a-site-is-an-unauthorised-reseller/p3

Also there is a bundle Superhot + Lords of the Fallen Deluxe + 1 Random Game for 2.99€ (around 3.20$) on https://gamerobo.com/ .

I bought a few bundles from them and never had any problems with it.

I've bought from them three times (I think).
Never had a single issue.

Purchased on HRK once, wasn't sure either...
Found this and read the conversation - quite old.
Still wasn't sure - decided to try and cancel my order if there wasn't a payment method g2a-free... I was able to pay with paypal without going through all the g2a bs.
As for the free key for buying some games - got not so great bundled games, but none of them were given for free.

To make it short : bought once - didn't have a problem

They are in the "shady/grey market" area, but considering it's a direct seller (not a "marketplace"), you shouldn't have big issues with it. I did purchase mostly make-a-bundle shovelware though, not single games, but for $2 you shouldn't risk too much.

The Superhot keys are from G2A, who somehow managed to convince the devs to supply them keys for super cheap. I have no idea how did they blackmail them to do so, but apparently all keys are legit. HRK is just reselling them. Which is ironic as fuck.

^

They are selling Windows 10 Pro OEM Key for $14 where it is both illegal to resell OEM keys and real retail price is $199. Add on top the G2A method of pay which even IndieGala admits was a fault, HRK is to trusted as your luck in any gambling game.

Anyone who says otherwise was just lucky enough till that they are not scxxwed yet. Totally agreeing on talgaby's comment.

Is HRK trusted?

Not exactly. Though I don't think they've ever revoked any games, either, so in that sense, they likely are.

That said, HRK is one of the most core sites in the G2A network other than G2A itself, and has often been a front-end for G2A sales. Meaning in this circumstance, HRK is likely selling left-over/additional keys derived from the arrangement G2A had with the SuperHot developers.
In other words, it's bound to be exactly as legitimate as the SuperHot games in the G2A bundle were.

Flip side, HRK has long been associated with the rumor of being involved heavily in bundle game resales, so they may literally be keys taken from the bundle in question (meaning they'd need to be activated within about a month, when they'd expire).