Dota 2 is churning along quite comfortably with integrated voice chat despite having more inter-region mixing. Any time this subject comes up the Dota 2 community nearly unanimously agrees that voice chat in no way encourages "toxicity" and more likely actually prevents it by assigning a human voice to the player as opposed to just disembodied words.
If anything it makes the game better when people start using voice. I've had games that I've given up on and people started using voice to ask for things like shared unit control for dominated creeps to stack ancients and actually communicate where they're going instead of trying to guess what's going on in four silent teammates' minds.
OTOH, I had one game on EU W where two Russians were talking (nicely) to each other and some British guy comes in and just says "I can't stand Russians. Good bye." and leaves.
And I've had my fair share of LAN cafe players with an open mic blaring music and their friends conversations. Mute and move on.
I really do wish we could mute the mic and not chat and vice-versa.
There's so much talk about toxicity in league, and very little about what CAUSES the toxicity.
Hands down the biggest issue is not coming down quicker on trolls and AFK's in ranked. They have a system in which they literally FORCE you to play out an hour long game when someone never connects, leaves after 5 minutes, doesn't get what they want so intentionally feed, and so forth.
For someone trying to climb that's automatically 2 hours gone. 1 hour for the game they're forced to play out, and 1 hour for the game they have to win to even out their ranking loss.
I have literally seen streaks of 60-70% of games with one of the above (troll or AFK). Eventually people get frustrated by it and that's when the toxicity starts.
If Riot wants to improve toxicity they need to protect the ranked experience better. I have so many things going on in my life that losing 2 hours because some asshat on the internet decided to troll is just not worth the time. 2 hours is a LOT of time, and while I loved the competitive nature of the game, eventually I just walked away from the game.
Shortly after I decided to walk away from the game, I came across the following video, and it describes EXACTLY why I stopped playing, and where my frustrations with the game where.
https://www.youtube.com/watch?v=5UfO7qOHx5M
The day I quit was when I sat down on a Saturday to spend playing league (one of those rare days where I got to do what I wanted). I spent 2 hours waiting on dodges (where it makes you wait when you leave during champ select). I kept dodging because I kept getting trolls in champ select. And then something like 4/5 of the games I did get into had either an AFK or someone who got pissed off in game at someone and started trolling.
I just thought to myself, what am I doing? There are so many more productive things I could have done today, this game does nothing but frustrate me.
I haven't played a game since, although I still watch LCS.
If you abandon 2 ranked games you get put into the low priority queue and have to play a certain number (at least 5 I think) of all-random games that don't record anything.
If you get reported for communications abuse enough you get a communications ban and can only use the chat wheel and rate-limited pings. Other reports get turned into low-priority queue time (supposedly).
If you dodge a game (even if you don't ready up) you get progressively harsher queue timeouts. It goes something like 4 min, 10 min, 30 min, 1 hour, etc.
There is also rumor of a hidden queue pool of toxic players. Kinda like a shadow ban but it lumps all the ragers and dodgers and AFKers and feeders together to play with each other.
Honestly, LoL never appealed to me. Every champ is about the same with about the same skillset and every game has the same laning. Riot seems to not really be able to make changes and their community management is bad.
If you can get past the turn rate and inability to spam spells in Dota you might enjoy Dota more.
No one was using it because it wasn't as good or easy to use as already existing third party programs, so they dropped it. Riot is probably thinking the same, and can spend their resources elsewhere on something that isn't already done better by someone else.
Contrast this to LoL where you're dropped into a game randomly with others random players for <60 minutes who you don't know but are forced to communicate with to maximize strategy. Communication is utterly critical yet the best option for doing so is slowly typing a message in a micro intensive game or a nondescript ping. The resulting player behavior is exactly as one would expect.
EDIT:
Are there any articles like this on the architecture of Dota 2 or Steam?
Players aren't consistently using voice chat since it's not built in. If you are in a match up where one team is on voice chat and the other is not; the team with voice has a huge advantage as text chat is less visible and has more delay.
Although the mute system is still a must have.