Gambit matches sure are long.. If you want them done as fast as possible, just loose the rounds.. Keep it a 2 phase match and let the other team win. Only kill adds and pick up orbs during the 10 matches.
That's the problem with completion steps. Wins don't matter so it's much easier to throw matches. That's the mentality mindless grinds like these bring. Why waste even more time trying to win when all that's needed is orbs gathering and completions?
If you could do seperate pieces, you could focus more on efficiency and would actually encourage more players.
Just look at the amount of AFK'ers with a macro set so they don't get kicked. Can't really blame the players though for a tedious grind introduced by the game dev.