Seal scrolls aren't guaranteed to give great ninja. I've heard to wait and unlock stuff at levels 50 or 60.

The Great Ninja War is an event. I've never played it, but it's in the same category as the Kyuubi Invasion and the Sannin thing, so I guess it's similar.

Okay, so I'm on level 53 now and I have Tendo Treasure unlocked. Overall the ninja obtainable look better - there's Pain paths, Jiraiya Sage Mode, and Hashirama. Only problem is I've seen so few people with any of these (I mean, it's a month-old server) so it seems like it's likely you'll get Kakashi Beheading Sword or Zabuza 7 swords (seen both on players) instead. Also they're all offensive as far as I know; the tanks like Kisame, shielders like Konan, and healers like Tsunade are all in Seal - so basically more variety.