What people seem to forget about the DRG-1N is that, while it is somewhat underwhelming in regards to firepower, it's meant to and was used en masse. The old school Dracs used to run these things in pure Companies and Battalions, where sheer numbers made up for their deficiencies. Not to mention that the Dragon was used in place of Medium 'Mechs that other Houses used to run, while heavier 'Mechs like the Archer, Warhammer, Marauder and BattleMaster would be then concentrated in what would be their more traditional roles in Heavy and Assault Lances, Companies and Battalions. Compare them to the most common Medium 'Mechs of their traditional enemies in the Federated Suns: faster and heavier armored than both the Enforcer and Centurion and with superior endurance to both (40 rounds of autocannon ammunition compared to 20 for the Centurion and a very pitiful 10 for the Enforcer), plus greater range and the ability to mostly dictate said range unless in extremely tight terrain. Hell, even against the Lyrans their speed would cause merry hell on their much slower and heavier formations (not to mention poorly led due to the prevalence of "Social Generals"). While they wouldn't be able to last fighting toe-to-toe with them, they could certainly give them a decently bloody nose, or simply skirt around them and hit weaker targets.
The DRG-1G just makes a dangerous 'Mech even worse due to the heavier punch of the PPC. My only beef with it is that, rather than install a third extra heat sink that would allow it to cool down while maintaining a running pace, a second laser was added to the after arc, which would force the pilot to slow down to a walk to cool off after firing both main weapons.
Also, as for that much disparaged aft-mount medium laser(s)? How many 'Mechs mount something facing in that direction? It's there for insurance and peace of mind. While a laser (or two) certainly wouldn't cause a knockout blow, it's enough to actually get some damage in (especially if they're within the minimum range of their autocannon or PPC depending on the model) where most 'Mechs would be unable to respond.
Honestly, back in that era when you should be able to see massed numbers of Dragons, it would have been a very scary prospect simply because of the fact that 1) they're very fast, 2) have very good armor and 3) would be using that speed and fresh, heavy armor in large numbers to hammer already weakened positions caused by their heavier elements or having simply skirted around the main line to hit a weak spot from the flank or even the rear.