I take it combo you have in mind is [stealth in close ->TD Boss -> snipe down boss-> TD zaps adds in immediate area -> pick off stragglers]. I think that works against the strength of a sniper build since activating TD will break stealth (a requirement for activating Snipe) and take you to 10 squares away from the boss at max range- that's half the max range of a sniper, 4 closer than the optimal range, and more than enough distance for the adds to close the gap on you if they survive TD, or are just outside of its range. idk if there's a known synergy between snipers and metathermics abilities that Im unaware of here but Im unsure it's the best choice for a sub-school in combo with snipers; MT is moreso a damage school and snipers rarely want for damage once their setup is in place. I personally prefer TC with sniper since it requires minimal point investment (outside of an Overload build) and provides some great utility even at 3 Will. Throwing is also handy for consistently landing torches and flashbangs/stingballs, so I think extra points not spent in MT would do better in throwing.
As for trimming pickpocketing, youre completely right. ~90 effective is enough to multisteal from everyone who isnt Coretech or Aegis, and for them ~110 should be about enough to grab one from each. You could also trim lockpick a little; the highest modifier items can give to your lockpick is +22, and with certain clothes that becomes +32, so the effective skill doesnt have to go any farther than about 110.
One last thing, about All-in; maybe Im just stupid but I had a run where I was depending on grabbing one to meet an INT check and no matter how many times I checked back at DnD it was never being sold, so I wouldnt depend too heavily on it showing up.
