Voice gives an edge, but they lacked even basic team coordination that should be a given without it.

I'm not saying you should play the game for him. Can't be bothered with a play-by-play, so I'll just comment on the single most noticeable mistake I saw in terms of teamwork:

At 05:15, you attacked top right corner with Fencers. ATOSTIC had five Glaives, two Reavers and Knight just standing nearby, letting your Fencers fail their attack. Now if we keep the bar high, lacking team awareness and not following up on you was ATOSTIC's mistake, but if we lower the bar a bit it becomes your mistake as well. You should've pinged the area and written something simple like "go"; that should've been plenty for a high level player to follow up on your Fencers. Pinging doesn't take that much time either.

There were multiple similar instances where the slightest amount of written communication (a ping with a single word) would've been extremely beneficial. ATOSTIC made considerably more bad moves where teamwork is considered than you though.

honestly i dont think you could've won in this matchup,i would give your team a 10% win chance maybe less