MTGNexus

While we don't have a top tournament finish since rotation to Throne of Eldraine, Aaron Barich held the #1 position on Arena for a while with this list.

Martin Juza wrote this article about making it to #3 on Arena with Mono-R and farming Golos Fields along the way.

Here is a Reddit thread about the latest iteration: Anax, Phoenix and lots of Embercleave, go! I guess Reddit User jsilv is Josh Silvestri. He talks more about Mono-R at ChannelFireball here.

Andrea Mengucci posted an here for CFB with an interesting mono red list in it.

I never put much time into the list as it's always felt weak but I might try it again with a newer meta

A followup from Josh Silvestri at Channelfireball with 3 updated Mono-R lists.

The "Bigger Red" list he had there was interesting and something I can see myself trying

Andrea Mengucci takes a look on channelfireball here.

Bobby Fortunately (top 4 SCG Team Open Philadelphia) makes a case for "Small-Red Aggro" on Channelfireball.

looks like mono red did well at the World Championship. was it players meta gaming against each other or if it was actually good

Apparently, Mono-R is good. Nick Prince here and Aaron Barich (on HardcastMTG) seem to agree that it has a sneaky combo-ish strength. I played the Mengucci-Manfield version in the Arena event and it was fine. It didn't seem fantastic, though. I mean, you can't complain about tier 1, right?

Seth Manfield posts a deck guide about the Mono-Red deck that he and Andrea Mengucci played at Worlds on Tcgplayer.

Andrea gives his version on Channelfireball.

I think the Manfield/Mengucci list is pretty close to optimal, though if you're facing less control you may want to tweak it a bit (fewer Anax, more Shock, etc.) Embercleave is really good, it wins games that you wouldn't win without it, but it can also cost you a game if you have two in your hand (it's Legendary and almost never gets removed, so the second one is a dead card, and more importantly it's not a creature, ideally you want to be able to attack with three creatures and cast it for 1RR.) I like that it can win against all of the other decks - I guess Jund or R/B is the worst matchup? - but there's also not really a matchup where it auto-wins.

Seth Manfield updates his take with video here (caveat: I haven't watched this video).