I have thought about these feats a lot and would like to throw in my thoughts. I would just like to make clear what they give you first to weigh the advantages.
Adder Strike
1. Apply poison to 2 body parts as a swift action
2. Use ONE dose of poison for TWO uses
I think it is important to make that distinction clear, since point 2 has a huge monetary effect of getting two poison uses out of one dose, and is possibly the best advantage of these feats
Pinpoint Poisoner
1. Apply poison to 2 blowgun darts as a swift action (drawing these darts is a free action) (still one dose for 2 weapons)
2. Attack with one as a standard action. attack with both as a full-attack action.
3. These attacks are considered melee touch attacks
4. They deal 1d2 damage plus any bonuses you gain on your normal unarmed strike damage, and they deliver the poison.
5. Throw such darts as if they were shuriken, making your ranged attack rolls against the target's AC.
To discuss these points:
2. It seems to be clear that pinpoint poisoner only allows you 2 attacks with a full attack action. However as per 3, they are melee touch attacks and therefor attack the opponents touch AC
4. It also seems clear that you would only do 1d2 damage + strength and feat bonuses,etc., and NOT the unarmed upgrade damage. The name of the feat would suggest you are actually holding the dart like a precision instrument (like you normally hold a throwing dart or pencil) and using it as such for precision over power to bypass the enemy's armor, as it also suggest by the fact that you are making touch attacks with them, not melee attacks.
5. When throwing these darts as shuriken, can you use flurry of blows with the darts and then shuriken for the rest of the attacks? If it says "throwing them as if they were shuriken" This is exactly what a monk would do with shuriken if he had a full-attack action. Also, as a monk you can interchange flurry of blows with flurry of shuriken, so is it possible to be adjacent to an opponent and throw the darts, then finish with blows? If this is the case, then it also seems reasonable that a monk with flurry of blows could forgo the melee touch attack feature of these darts and do a flurry of blows with them while holding them as weapons, even dropping them after the first two strikes to get full damage on his successive attacks. Since this whole point is debatable, I will not continue with it as fact, but would like opinions on this.
What are the advantages to take pinpoint poisoner in addition to adder strike?
1. Use injury poisons over contact poisons, which generally have faster onset and of which there is a greater variety.
2. Melee touch attack against the opponents touch AC
3. Throw the darts in the same round you poison them.
What are the disadvantages?
1. Can't use flurry with the darts.
2. do less damage
How can these be bypassed?
Use adder strike with spiked gauntlets or spiked brass knuckles. (These do not exist, but are not without the realm of any kind of possibility and could easily use the same weapon proficiency as brass knuckles, which monks are proficient with. This I feel is very reasonable). With this you can use flurry, and still use injury poison.
Lets look at some combat examples using both.
Adder Strike
1. Combat starts, apply poisons, move to an enemy in range, attack with one poison. Round 2, Flurry opponent with one poison. Round 3, apply poison, provoke attack of opportunity, flurry
2. Combat starts, apply poison, delay till an enemy is adjacent to you, flurry. Round 2, apply poison, provoke attack of opportunity, flurry
Pinpoint Poisoner
1. Combat starts, apply poison to darts, move next to one enemy, attack with one poison melee attack. Round 2, drop your second needle so you can flurry.
2. Combat starts, apply poison to darts, delay till an enemy is adjacent to you, attack with both darts.
3. Combat starts, apply poison to darts, throw them as shuriken.
There seems to be some problems here, and that mostly comes in the form of provoking attacks of opportunity from applying poisons in combat, and the one advantage, applying poison as a swift action, rarely seems to pull off like you'd imagine.
In the adder strike examples, the best option looks like 2, but regardless of what you do, using the feat again in combat will provoke attacks of opportunity, so the bonus of using it as a swift action seems kind of nullified, as there is no real practicality in applying a poison swiftly to get attacked. If you DIDN'T have adder strike, and say you were jumped and unprepared for combat, you could move away from opponents, apply poison as a standard, and wait for them to approach and attack in the second round. You are still using poisons, only you are delaying for a round and not get attacks of opportunity since you are not tempted to apply poisons in the heat of combat. Really I feel like point 1 of adder strike should be "Apply poison to 2 body parts and provoke attacks of opportunity as a swift action"
In the pinpoint poisoner examples, it looks like option 3, throwing them is always your best bet. The only other case would be to poison and weaken a monster with a really high AC and really low touch AC. But such a creature is more than likely to have high fort saves as it's a tank type, so how will this really pay off? Pinpoint poisoner might be really great if you could do flurry of blows and flurry of shurikens with it, but with adder strike, you get spiked gauntlets and you can use those injury poisons with flurry right away. OR don't bother with Adder, and just apply them as a standard when you know you are going to go into combat, or right at the start if you think you'll need them.
Really I think these feats look cool on paper, but don't really deliver in any practical way.