I actually brought this up in IRC last night as well, and completely agree.
In addition to the TANKINESS of The Rook and Oak (as well as a non-Summoner Sedna) Three of the four Light-side Demigods have skills that are centered around taking down an enemy Demigod with extreme speed. The Rook has Hammer Slam (which doesn't have to hit directly), Reggie has ungodly amounts of damage output, and Sedna has Pounce. Oak has a solid DPS, the ability to shield himself from damage, and the ability to heal like a madman.
Simply put, the Light-siders are focused on eliminating the enemy Demigods. And in the meantime, they have a pretty solid amount of ability to deal with enemy Creeps (which you can completely let your creeps deal with if you keep enemy Demis pushed back)
The Dark Side is the side of the Glass Cannon. Torchbearer has plenty of methods to control enemy creeps, and some GREAT stunning ability... but he's about as soft as Sedna's pet's underbelly (I would've set Catapultasauri, but I imagine with the ability to use their tail as a catapult, they must have some very strong abs). Erebus suffers the same problem as TB. While he has great crowd control abilities, one sight of a damage-focused enemy Demigod and he's sent running for the hills. And without Bat Swarm or some kind of increased speed item, there's a good chance Oak or Reggie will run him down.
Then comes QoT. She's another great anti-Creep, or even a great Siege if you build her that way. But, short of her Bramble Shield, she's got the same problem as the other two. Bramble Shield is a great skill and all, but it can't carry her the same way as just being a walking castle can.
And I don't have enough experience with UCB to judge him, but he looks like a slower, weaker, DoT version of Rook with faster attack speed.
But at cursory glance, it definitely seems the Forces of Light brought a much stronger set of candidates for the throne vacated by the Progenitor than did the Dark.