I've played 5 or so in game, but I favorites Ivy and gotten her the vast majority of my matches. I've messed around with all of em in Sandbox mode though and only find a few to be my style.
LMFAO thats fucking crazy. The one button server pause is super busted to begin with but I can see that being super useful for cheesing things like urn like you did. Jesus
I have 100% noticed the matchmaking is still rough. I've won all but 2 of my 12 or so games so far, yet I'll still get people on my team who go 0-18. Just keep grinding and you'll hit those high MMR stomps where your team still stinks :P
I've had the same thing happen during sandbox where if I switch heroes using the alt tools, the build defaults to that. Definitely annoying, but usually just clicking "browse builds" again solves the problem.
I had this happen to me in a game a while ago. I was solo laneing and me and the enemy both basically just had to sit on our guardian because it was unplayable for a good 45~ seconds.