That is correct. Cleave gives you the ability of damage to an adjacent location, and reaping strike allows dealing of damage even with a missed attack roll. But they don't deal lots more damage than a basic melee attack.
Personally, I prefer the 4d6 rolling. Using a set point buy / standard array make it feel too cookie cutter for me. I like the RP that comes out of having large deviations in scores. But I also suggest, like it says in the book, setting some limits (mainly a lower). I still want the players...