In the video hes not in plain sight tho, hes in total darkness. Theoretically he doesnt even need to hide for this unless those skeletons have darkvision within range. Either way they should be moving towards where the Eldritch Blast is coming from.
That's true and I'm going to check how the AI treats stealth now, cause they buffed it with the last patch.
But there is one problem still staying for sure - he's not supposed to be able to use Eldritch Blast and hide on the same turn by RAW. That's too OP. For a rogue the ability to both attack and hide is a way to mitigate the fact that he's not very good at tanking and may fight on the front lines at the same time and the way to buff his attacks, while he uses fairly weak weapons. And here we have Warlock, who can stay away from his enemies and keep fighting and uses Eldritch Blast which is quite powerful as it is.