Hoban almost had a second on the 15-minute mark when he latched on to Benjamin Buchel's long ball forward, only to nod his effort narrowly wide.
Dagenham's first sight of goal arrived midway through the first half, but Buchel was equal to Matt McClure's long-range effort before Ashley Hemmings saw a strike of his own deflected wide moments later.
Mark Cousins was called into action at the other end just before the half-hour mark as he denied Alex MacDonald's 25-yard strike, while MacDonald turned provider later in the half to set up Hylton, but once again Cousins made the stop.
MacDonald would get his name on the scoresheet after the break, however, as Oxford began the second half much like they had the first. The midfielder thumped a volleyed effort into the corner from the edge of the box to give the League Two high-flyers a cushion.
Dagenham, winless in six coming into the match, went in search of a route back into the contest and nearly found a quick reply when Cheyenne Dunkley twice spared his keeper's blushes in quick succession by clearing the ball off the line after Buchel had been beaten by crosses.
The U's soon regained an element of control, however, and both Hylton and Hoban came close to adding a third to all but seal their place in the next round of the competition.
The Daggers, who currently sit bottom of the Football League, would not give up, however, and Oxford needed two saves in quick succession from Buchel to keep their two-goal lead intact as the keeper denied both Hemmings and Joss Labadie.
That was how it stayed as Dagenham's winless streak was extended to seven games, while Oxford will await news of the next round's draw, which takes place on Saturday.