Ns blade caledonia spec

I think the first biggest red herring you'll face is Creeping Death, the level 34 followup to PA which is the actual stun in that chain. The problem is that even assuming RR2, getting this plus composite 34 stealth and composite 31 envenom (snare, only poison between 30 and 35) will leave you with about 94 spec points for weapon and CD combined, not a good look. That could get one of them only as high as 13.

The second red herring is to get the blades after-evade followup at 29. This is one of the benefits of blades over piercing, other than the obvious armor table advantage; its after-evade stun followup is much lower spec than pierce's 44. However, while the result isn't quite as distorted as in the Creeping Death scenario, it does leave dismally few points for CS and CD.

The solution appears to be to focus on using the garrote / achilles' heel chain from CS at 25 spec, presuming RR2 (which you'll be pretty quickly if you weren't there already) and getting composite 34 stealth (26 base) and 31 envenom (23 base).

With the remaining spec points, you could get the after-evade stun from blades at 21 or the side stun from CD at 18, but not both. You'll have to decide which is more important, or perhaps you could back off envenom a little bit to get both -- 21 base spec envenom allows both stuns, but you won't quite reach the level 30 DOT. You will reach the level 29 ws/con debuff. (Reducing CS would be another option, but garrote alone is going to use more endurance and deliver fewer results, plus lower PA and growth damage.)

I personally suck at forcing positionals and would personally opt for full envenom and 21 blades, but if you're good at it then you're certainly better off forcing a stun rather than waiting for one.