Keep in mind that 'real' artillery (late industrial/early modern) could shoot very very far. So a 'range' of 3 is ok.
If you're looking to 'balance' archer/ranged units, then the key thing to do is to remove the minimal one damage/shot. The calculation would need to allow for zero damage shots, which IMO, is key to finding the right balance.
(archer vs. GDR - GDR shouldn't die)
This also means that as city strengths go up (better defenses/more modern) then older ranged units won't do any damage, so you must upgrade or walk away.