Disinformation
Blink Blink 
The original beta version of Ariel was rumored to be a nightmare, that version of beta Atomos sounds like the Devs said “What rumor can we release to trace our Beta leakers”.
Edit:
Looks like an advertising mock up.
My favorite advertising mock up is Natalya freezing enemies in a mock version of Empires you could play for 30 seconds.
Okay
Please everyone who gets Atomos send him to my account.
Slow Heros
I would not want to face a very fast mana speed Atomos ( rumor this is possible in challenge raids when Weekly rule is Rush Attack ). Very fast and fast will always dominate raids.
But I would easily take him to 5* 2.60 at slow speed.
As long as he revives, you can still do matching/ tile damage and you can use Miracle Scrolls- which still suck ( but it is what it is ).
Boss Heroes
People complained that Wonderland was hard - will get harder with fixed Hatter - because it was designed around its heroes.
Atomos, like Kong, are examples of Bosses converted to heroes.
RNG
While I would prefer Ariel or Aeron ( together they fight crime), I would take 2 Atomos.
Titan OSOK
Luckily I am in an alliance not fighting 14* Titans, but Atomos seems tailor made for high level titans unpredictable one shot one kill.
Wound seems most useful against titans and his damage increase is easier to time with titans huge mana bar.
Improved version
Personally I would just change his attack to splash damage since I think his primary roles will be against 1-3 remaining opponents, bosses or titans. Unlike Alberich and Mother North who work well against 5 opponents.