A̶l̶a̶s̶,̶ ̶I̶ ̶h̶a̶v̶e̶ ̶r̶e̶t̶u̶r̶n̶e̶d̶ ̶t̶o̶ ̶b̶e̶ ̶g̶r̶a̶n̶t̶e̶d̶ ̶a̶u̶d̶i̶e̶n̶c̶e̶ ̶o̶n̶c̶e̶ ̶m̶o̶r̶e̶.̶ So this thread's still open and it's been a hot minute.
Genshin seems to have had a bevy of revisions which convince me that the result is yet still mixed. Though I'll change my vote to Incon rather than a Childe dub.
Elemental Energy now seems to cover a much, much wider array of forces than previously, which leads me to believe that with elemental sight it would be possible for Childe to perceive Mana. Which would massively increase his chances, being able to perceive the things he needs to dodge, block them with better efficiency, or cut them down.
Additionally, his resistance to Abyssal Energy should grant him a similar, if not greater, resistance to the effects of Mana's nastier side-effects, if he does get hit.
Which is still probably not good for him, while he upscales, his 7-A value doesn't appear to have changed so still pretty much a 1.8-5x disadvantage, which leads to-
Halloween, another person entirely. An interesting case, as it makes this a two-on-one. I will never argue a skill debate, but I'll take her pages Gifted vs. Childe's Genius combat intelligence and say that in CQC Tartaglia has the upper hand in Skill even with an AP and Lifting Strength Disadvantage.
Her presence affects my initial assessment of the fight, with Childe's abilities he should be able to deal with a less skilled melee opponent fairly easily. Even just blocking Elemental Attacks still causes the defender to be affected by the element, which could result in a cruel Riptide-Electro Shock paralysis combo that downs her quickly. Or she could be a nuisance that plays keep away with Tasha preventing him from getting to good a shot to bring either down.
However, Childe's mobility options also make him an equally difficult foe to pin down as he can simply Blink out or use his intangibility to break free of bad trades.
Again two vs. one is a difficult prospect but without the ability to hit him, it seems like he can just kite forever and due to the nature of the fight (him being at a disadvantage), he's much less likely to play stupid.