You have a CPU OC'ed from 3.3 to 4.7 that has a TJMax of 91C and after one hour at full load you are at 70C. I would say you are doing great. You have 21C headroom after a decent OC. Without knowing your delta T on your water in / out and water out / ambient it is hard to say if you could do any better. Remember there is no set temp for water cooling your rig. It depends on how good your fans are at pushing air through your rad, dissipation quality of your rad, room temp, quality of the mount, etc.
You should be looking for two things:
1) Is the temp at full load at your OC well below TJMax - yes yours is, you can stop here, the rest doesn't matter as better load temps will not improve your OC.
2) Is the water / air delta < 5C - then you cannot do anything but lower room ambient to get better cooling, your loop is about as efficient as it can get.
As a side note you can look at water / water delta to see how efficient your rads are working. in conjunction with the air / water delta.