I dont knowww :D
I did mixed in the end, 3 scatter 3 traps, and I'm not entirely satisfied.
Scatter at 5 can be usefull against both melee and ranged classes, whilst at 3 only vs melee, but traps at 5 rocks hard, you can put 3 at the same time and they last FOREVER, so it's a pity totally giving up on traps. At 3 they do their work (2 traps at the same time), but there is a big difference with traps at 5. Scatter at 1 is shit, stun time doesnt last enough time to use any skill before the enemy is back on you already.
Probably the most conservative choice is scatter shot at 5 and ♥♥♥♥ it.
If you are high amped maybe you could try something weird and have bless 5, traps 5, scatter 3, power shot 3. I dont play ranger as main char anymore so I'm not making experiments.