Well first of all for an operative this spec is not ranged at all, only your corrosive dart and grenade have a 30m distance, your cull and weakening blast is around 10m. Lethality provides pretty decent AOE and ok single target dmg. You just need to learn to still use hidden strike, backstab and shiv for Tactical advantages for cull. It gets tricky to maintain energy and TA's for this but once you get the hang of it you can easily be top 1-3 in dmg. This is a support spec so dont expect to drop healers or solo nodes with it. You'll put up good numbers and do well, but you won't drop healers or single targets anywhere near as quick as concealment can.