I've had some bugs on 360, which is normal, since I've put A LOT of hours into this game, but nothing remotely coming close to ''fuck this game'' rage.
PS3 version might be more problematic.
As for an all Sniper team, here's my report:
My first attempt was a disaster. I tried putting 3 snipers on flight duty, spread across the bottom of the map. It didn't go very well.
My second attempt turned into this:
One Archangel Sniper with disabling shot and double tap, the classic sniper role for a regular team. No point in having more than one.
Two Scout Snipers, with Snap shot, gunslinger, sensor, in the zone, scopes and ghost armor. Before they reach Colonel, The pistol was the better choice 99% of the time. But in a clutch, being able to move cloaked and take a sniper shot might be the only move you have left in a turn. Since they can flank easely, I gave them In the Zone.
Three ''Sniper Ball'' Snipers, with squad sight, double tap, a mix of either sensors or disabling shot and ghost armor.
These guys follow the scouts, and take shots at whatever is discovered. Pretty basic. If a scout has discovered something and has to run back, they can toss a sensor to keep LOS. Ghost armor to get crit% when headshot is unavailable, for the grapple and to get in position without getting shot at to take a shot next turn at a dangerous unit like Sectopods.
6 snipers is far from perfect, but fun to try. No point in giving anything but scopes, since you don't want to miss any shot. That team suffers from lack of explosives, and high %ToHit and damage up close. SURPRISE MOTHERFUCKER! enemy groups that pop in the middle of your team can be a bitch.