Expert Sniper basically is a bunch of agility plus a bunch of longarms firearms skill. The also makes you very good with a shotgun, so you have a option for situations where true sniper shooting is not practical. I have just recently returned to the game, but I think I am finding that building a character is a balancing act between specialization and some utility/secondary abilities. Everyone in the group should be very, very good at something, but they should also have a minor interest or two. Be moderatly good at a couple of things other than pulling the trigger (you could be a infiltration guy, or the medic, or some outdoor skills, etc, basically a second expertise that can come up once in a while) and keep a shotgun in the van.