Gareth Wyatt notched an early Dragons try but two Contepomi penalties put Leinster ahead before the Argentine star danced over for two great tries. Richard Fussell's try then reduced Leinster's lead to 20-13 at half-time, and tries from Christian Warner and Gary Brown ensured Leinster's bonus point.
The Dragons, captained by flanker Jamie Ringer for the first time, troubled the hosts early on and full-back Wyatt charge over for a ninth-minute try after good work by Hercus and Paul Emerick. However, Hercus missed the conversion and Leinster soon took control.
Contepomi cracked over two penalties - the second after Dragons hooker Kieran Crawford had seen yellow for coming in at the side of a ruck - to nudge Leinster in front before Hercus landed his only penalty success on 29 minutes.
The Leinster fly-half then took centre stage by dancing past eight would-be tacklers before crashing over for an outrageous 33rd-minute try. He converted and then seven minutes later, Contepomi linked with Warner before skating around four defenders to notch his second try.
Paul Turner's men hit back in injury-time when numbers out wide on the left saw winger Richard Fussell evade Luke Fitzgerald's grasp to dot down. Hercus missed the conversion and he squandered a crucial penalty chance just after the interval.
Warner's try on the hour was set up by a clever Contepomi pass and Brown notched Leinster's fourth touchdown after easily evading Fussell's attempted tackle.
Leinster: Fitzgerald, Brown, Lewis, Warner, Hickie, Contepomi, Willis, McCormack, Blamey, Pala'amo, Finnigan, Toner, Keogh, Gleeson, Heaslip
Replacements: Berne for Warner (58), McCarron for Hickie (67), Dunne for Willis (76), Vermaas for Blamey (64), Corrigan for Pala'amo (41), Ronan for Heaslip (73)
Not Used: Byrnes.
Dragons: Wyatt, N. Brew, Emerick, Smith, Fussell, Hercus, Walker, Black, Crawford, Harrison, Hall, Sidoli, Bearman, Ringer, Fitisemanu
Replacements: A. Brew for Emerick (63), Warlow for Hercus (64), Ireland for Walker (60), George for Harrison (76), Griffiths for Sidoli (58), Daly for Fitisemanu (31)
Not Used: Charvis.
Referee: G Hannah (RFU).