Ok, I won't explain why x1 shot sniper sux, and won't say that 12 AP sniper is must have, but still there're perks in-game that simulates more points than any other, Weapon Handling is one of them, it gives to you 3 SPECIAL points if you're not going to loot encounters (you'll have low carry weight), so if you aren't going for 6 ST (Stonewall perk), then make it in your case 2 ST, if you're going to use jet, then 1 ST. More Critical perk just gives you 5% critical chance, it's must have perk for bursters and arm-cripplers, it almost has no effect for double shooting sniper and very small effect on snipers. It equals to 1 LK for standart sniper, so if you're not going to 2nd toughness or x1 BRD on 6th level, then pick More Critical, and this is enough if you're not crippler/burster.
Logically you can see that even with 10 LK and x3 More Critical you'll have only 85% critical chance in the eyes.
While with 8 LK and x1 More Critical, but 12 AP you'll have 2 shots and 89.89% that atleast one of 2 will be critical. I'm not sure how much % gives that x1 MC, don't want to calculate again, but practice shows me that I wasted perk slot on it, and it would be better if I took 2nd toughness on 6th level, screw this more critical.
Focusing build on constant things based on rolls/real life luck is better than maximizing rolls. Making lots HP and x2 shots per once is better than stupidly increasing chance of critical.
5 ST is really useless, 6 is good +8/10 EN, if not 6, then it better be low.
Lifegiver - on 12th level simulates ~6 points, the best damn perk ever in game. It's like Small Frame trait or Good Natured trait which simply can't be ignored.
More Critical - for bursters simulates 5 LK, with base 6 LK it roughly increasing chance to do x1.5/x2/x3 damage in two times, other 2 MCs will increase it in two times again, so x3 MC will make critical bursts x4 times more frequent, while for sniper it equals to 1 LK, it means with this crappy more critical perk your chance to score critical will be increased in 1.07 times (for 10 LK sniper), hell yeah! In 1.07 times! Damn it! You fucking wasting your perk slot just to score criticals in 1.07 times more!
Better Critical - must-have perk for anyone who's going to kill people, can be taken if you have atleast 6 LK, if you have atleast 6 LK it means you're going to kill people, so it worth even for bursters, if torso-critical tables are the same as in Fallout2 for damage multipliers, it'll increase average critical damage on ~30%, while for aimed shooting snipers I don't need to explain what does it mean, because it's obvious, well... you're going to score criticals... of couse you need this perk.
Weapon Handling - just gives 3 SPECIAL points into ST which doesn't give you carry weight, but also can't be reduced by jet, and of couse you simply need jet if you're going for x2 shooting. Yes, you'll have -20% to hit with rifles, but don't forget that 1 ST means you have lots points to spend, and these 20% can be easily negated (if you want to negate them, because shooting with 80% to hit in the eyes on max distance isn't that bad really, if you compare standart build % to the same but with -20% to hit). I just want to say that ignoring such perk as Weapon Handling is the same as not taking Small Frame or Good Natured traits when creating a character. If you're not burster, then weapon handling takes 2nd place in perks by quality, 1st and 3rd is lifegiver, on 12th and 15 levels.
BRoF - you simply has no choice, you need it for x2 shooting.
Toughness - if you can live without awareness (if you're not paranoic) this is the only perk you can take on 3rd level and may be on 6th too, because you won't see this 5% critical chance on practice by shooting heads and eyes, while toughness is passive perk which is always active and works good vs bursts.
Try to make 10 EN, but if you really need 10 PE, then 6 EN is max what you can do, well yeah.. you're sniper, so PE is better for you, simply it's cool when they bursting you, sniper, and you live longer than burster and then shooting 2 times in his eye and, of couse, both crit ^_^ If you don't like being terminator with 244 HP, then ok, take your 6 EN.
perks are obvious: toughness, toughness/MC, BC, LG, LG, BRoF, WH. With 6 EN you'll have only 196 HP. Jet is easy to farm, and 30 minutes is very very long, nuka = 100 caps in JT, 100 caps = every NPC has some caps, farm jet, gather thier little ammount of caps, so you can supply yourself with these 2 drugs. At begin use 10mm pistol (because 10mm ammo is easiest to get, you can't even craft BBs so fast, as you can farm 10mm, Boneyard regulators are very kind, then will give you thier smgs and lots ammo, and also radios). If someone says 1 ST = problems in leveling, no, it's not true, I even took weapon handling on 21st level, because BRoF on 18th will help more and you don't need high skill to shoot in point blank in the eyes of poor molerats.
Oh, and if you want to talk to Sha Enin and other traders, or if you want to have a dog or female merc, then you can spend 1 point on IN instead of 2 on CH, so with 7 IN (+2 with mentats=9) you can have 3rd doc prof and craft mentats for you and provide yourself with permanent +2 CH and live on mentats.