Last 3 games final turn timer was less than 20 seconds. Both times I couldn’t finish my turn and it cost me the game. All 3 games my opponent either did the big hoggar pirates or khadgar tokens. Does their firewall exploit reduce my timer?
I remember having problems finishing my turns the few times I played on my GF's old laptop, or on my tablet. Perhaps the animations were slower during combat, and they ate up a big part of the turn timer. Never had issues on my desktop computer at my house, always have plenty of time. When there are many deathrattles and effects combat can still take a stupid amount of time.
I don't think your opponent disconnecting can have any sort of effect on your own timers, or at least it never did on the pc i usually play on.