Tobirama getting now the +30% permanently was pretty useless since 99% of the fights end before round 5. Very likely, as somebody pointed out, the first version was this one, and got changed later when the damage formula was changed too so that pvp battles would reach round 6-7way more often than now.
Btw, 15% chance to crit is better for water teams where most of the damage is based on ninjutsu (and was one of the reason why gnw tenten obscured him, not only for the round1 mystery and the triple chase).