I've been playing DotA since the mid-late 2000s, then moved to LoL, then DotA 2, then HOTS.
In my experience, flaming is considered worse than ruining the game and feeding. Why is that? Insults can be muted with a single click, if the bot feeds 0/5 by the time I have my ult I can't exactly pretend that didn't happen and proceed to play normally.
I've been only punished once for flaming, with a 40 some games of having an impaired communication ( which if you think about it hurts my team more than it hurts me ) but I've never seen or heard of anyone being punished for feeding intentionally.
Hell I did it a few times and quite frank when I was punished I wasn't mad I got punished, I was mad they didn't punish me for playing like shit and ruining games but they punished me for calling a bunch of feeders cunts. I mean what the hell, what kind of backwards SJW driven society are we in when words are punished more harshly than actions?
In DOTA 2 I'd report people of feeding and I'd sometimes get a message saying my report was deemed right, so at least there's hope.