Any thougths about me going the Wintertouched/Lasting Frost route as well? Is it worth it for a melee ranger? (I should be able to squeeze it in by level 14)
I don't know. Melee rangers generally have an easier time getting CA than archers due to flanking (though maybe not so much if you're going to be soloing a lot), the the Lasting Frost combo is mostly recommended for archers. Reckless or Bloodclaw on your weapon might actually do more damage, let me run some numbers. Note that Reckless and Bloodclaw scale, unlike Lasting Frost.
Assuming a base 50/50 chance to hit (and 1/20 chance to crit) for simplicity's sake, as I have no idea of the average AC for monsters at level 12.
At-will DPR with Twin Strike, no CA, Reckless weapon, Called Shot:
0.45 chance to hit, 0.05 chance to crit
Damage on hit: 1d10+18, average 23.5.
Damage on Crit: 3d8+28, average 43.5.
Average DPR: 2*(0.45*23.5+0.05*43.5)=
25.5At-will DPR with Twin Strike, CA, Cold Vulnerability, Called Shot:
0.55 chance to hit, 0.05 chance to crit
Damage on hit: 1d10+12, average 22.5
Damage on crit: 3d6+22, average 37.5
Average DPR: 2*(0.55*17.5+0.05*32.5)=
28.5So at this level, the Lasting Frost route would deal more damage. Of course, this is a purely theoretical numbers exercise (you won't be getting cold vulnerability on your first attack against any given monster, nor will you never get CA without a frost weapon). As I said, the cold vulnerability from Lasting Frost also doesn't scale whereas Reckless does.
Think of it as a physics exercise - assuming ideal conditions because it would be too hard to calculate otherwise, even though those ideal conditions will never come up.