They're gone from the current necron codex, however they still make appearances in existing lore. They seem to fight alongside necron units in one or two instances that I can recall, such as the necron forces in the Ciaphas Cain novel Caves of Ice. These can be confirmed to be pariahs since they reduced trained stormtroopers to gibbering cowering wrecks simply by proximity, something that even flayers didn't do. Therefore it is a safe assumption that they projected a soulless aura in the same way that psychic blanks and human pariahs do.
So, they still exist. But they no longer seem a common choice for necron armies to take. Another thing to consider is that they are human in origin, and it stands to reason that they require necron technology to exist. Given that they only appear in the recent/current 40k setting, it is therefore a safe assumption that at least one necron faction is responsible for their existence.
In the old fluff, Pariahs represented the c'tan's next ideal for the galaxy. It is entirely possible that this is still the case. Necrons fear the idea of free or rogue c'tan more than anything else and with good reason. We can confirm the existence of at least one rogue Deceiver shard due to the short story Deus Ex Mechanicus. It is also possible that the same or another Deceiver shard is the golden skinned stranger responsible for Abaddon's acquisition of the daemon sword Drach'nyen.
Rogue c'tan are confirmed. And pariahs are still technically part of the lore. I want to put these pieces together, and the most logical choice is a necron faction involved in the creation of pariahs. Whether this is in collusion with a c'tan, under control of one or simply a freelancing cryptek exercising his own curiosity. Either way, I'd like to see more of them. They seemed like too big a part of the impending End Times to simply discard from the lore entirely. Don't get me wrong, I love the newer necron fluff. But it seems there's a lot of potential surrounding Pariahs that simply isn't being used.
Does anyone else agree?
Nonsense is our Salvation