Llanharan failed to catch Maesteg on tries, being five short at 202-197, but their 46-24 win at Carmarthen Athletic gave them the title by three points.
Full back Marc Davies ended with 471 points - the highest by any player in Wales this season - and that included 24 tries, one behind fly half Mark Roper, while hooker Richard Emms crossed for his 20th try of the campaign and veteran
No 8 Colin Malone ended with 14 tries, having announced his retirement. Carmarthen competed well and fly half Julian Howells also retired after finishing the season with 322 points.
Whitland celebrated their best ever season - finishing third in Division One - with a 20-10 victory over visitors Brymnawr, who had lead 10-0 at one stage.
Fly half Aled Davies scored a try, two conversions and two penalties to end the season with 248 points. Centre Lee Glanville notched his 19th league try.
Brynmawr had a Craig Mapp try and a conversion and penalty from the prolific Jason Williams who took his season's tally to a massive 345 points.
Narberth and Rumney turned in an amazing game with 16 tries and Rumney leading at the interval, before the Otters pulled clear to win 61-37. A try hat trick by No 8 Kati Tuipulotu helped the home side power through to victory.
Also on the board for the winners was Simon Daniel who crossed for a try and converted eight of their nine touchdowns. The other tries came from Andrew Jones (his 26th), Deiniol Evans, Gareth Bennett, Jason Jennings and Craig Hawkins.
Rumney's try scorers were Joe Offside, Chris Jones and Mike O'Neill who all crossed twice with Anthony Jones notching one, while Carl Ford landed the lone conversion. Despite the possibility of relegation, Rumney should be proud of finishing with 105 tries.