So far, dark side has only come out ahead in a single pantheon tournament, with light winning almost every time. This time around with v1.1, dark is so far in the lead. This could be a fluke and light will be pulverizing them by tomorrow, or something that was changed in the most recent patch has flipped the odds.
1) Heart of Life nerf. It's possible that this item was more useful to light demigods than dark. Suddenly a tower Rook can't maintain his impenetrable fortress indefinitely. You aren't seeing Oak's shield/HoL combo as early in the match, if at all. Sure, the nerf hurts all demigods overall, but maybe light side is feeling its effects just a bit more strongly.
2) Number of players. This isn't quite as significant now, but light side used to have a lot more players. Before, bots were extraordinarily prevalent (they still show up now, unfortunately) and the side with bots is all but guaranteed a loss. If there are more light side players than there are more light side players fighting bots, giving them free favor. Now the numbers are a bit more even and there are fewer bot matches.
Any theories of your own? It could just be a fluke, you know. Dark has won once before and this current round is far from over.