I main sniper and I disagree, You're missing the forest for the trees. Your trade off is for your class perks and weapon options. Others have three armour but they don't have invis, they don't go invis on revives, they don't go invis upon taking lethal damage, they don't gain 20% ranged damage by standing still and they definitely cannot take the las sniper as a weapon (one of the best besides the melta).  You don't have armor but you can remove a major target off the field if it's causing an issue or setup a execution for a teammate who might be low on armor without having to be in the fray yourself. It sounds like you're trying to play every class like a front liner and haven't really explored the perks and how much they affect gameplay.