This is still an issue in 1.8.8...
I've found this issue to still exist in the current 1.8.1 Minecraft version, I've already posted a minecraftforum.net topic on this issue a while ago: http://www.minecraftforum.net/forums/minecraft-discussion/recent-updates-and-snapshots/2307527-1-8-1-8-1-default-scale-river-generation-in-large
Same problem still in 1.8.9