Killer Bee is only a plot reward at level 98 for clearing all the level 90 instances and the level 100 update to even get him will be months away. As far as spending on the Tendo pack just don't do it. Everyone who has him will tell you Tendo is useful but he's no longer that good in PvP. Also, as someone else pointed out, nearly every player that pulled for him got him at 800. So doing it at 400 is just a big gamble as well.

If you are going to save up and use those seal scrolls do it in any pack after sage. By the time you have saved up those 400 we will most likely have another new pack, likely the reanimation one. As such spending them in that or kage or just saving for an even further out pack is still much better. All of the pains are okay at best, sage jiraiya, beheading kakashi and wind blade asuma frags are given all over randomly and none of them are that great either. Hashirama is a monster and is definitely worth it but in terms of the 400 seal scroll wall I still wouldn't bother with it. I get that new ninjas are fun and enticing but the fun value goes down quite a bit when you find out that they just aren't that great and you wasted all that time and effort for them.