Odd, I had them exactly reversed. Generally the DPS reg seems to just not bring enough to the table, especially at rank 7, compared to a mine reg. In 2v2 combats, an allied reg can do strong damage to multiple enemies, often allowing your team to pull in major wins. Not just one kill, but two.
Also, mines with any stun mechanism becomes an impressive damage do-er, and with shrapnel mines, it ends with a massive snare, astoundingly good for ganking.
In comparison, the DPS reg is significantly more squishy, and tends to get focus fire + death in large combats. A well used batswarm + charm, a boulder roll, or some other effect brings him into melee... and he doesn't get out again.
Mines Reg is a purely defensive character whose effectiveness goes down as his opponents get better. Smart opponents will dodge them, trigger them with minions, trigger them under Shield, interrupt them, and will rarely get caught two DGs at a time. He can only get kills if his opponents are stupid or reckless, and is weak in pitched battles since his only good ability recharges in 10s.
DPS Reg is the exact opposite. He can chase for kills, he has excellent sustained DPS, and only becomes stronger in arranged team settings if his allies can cover up his weaknesses. In close games where the teams can handle eachother's bursts with good counterplay, irresistable DPS becomes the key.