I just had a game with the same problem.
It was a good game, we we're kinda even - it could be a close race!
Then we have a dc. At this point a /remake is way to late, but how about a /ff?? No - no such thing in Nexus Siege.
We unfortunately we're attackers, so we have to fight (for no reason, we cannot win a close game 4v5 - even though we did try) to the full 20 minute mark. Now it is impossible for our team to grab the victory, but we still have to defend.
Worst part is he actually reconnects now (after being dc'ed for ~15 min) and wanna fight. i.e. no open mid and fast ending to a bad game.
So another ~15min of my life wasted since i did not have the mentality to fight for him for a tie.
The worst part was not the fact I lost a game - most of the time the fighting is the good part - but I had nothing to fight for - no hope.
No the worst part was the fact that I turned into one of those raging/flaming sons of b****es who was mean for no reason, kept feeding for no reason - because i just wanted the fight to be over fast so I could go on to something i find meaning in - a fight were i can find hope.
Now I'm too scared to enter a Nexus Siege game again - 'cause I have to fight a 4v5, I can't just /ff and find a better match, even though the remaning 3 wants the same. And well.. a 4v5 with a dc on enemy team is just as bad for me!
I want the close matchups were every team-mate counts, not the "sit around and wait for 30 minutes even though the game is already decided"-matches.