Archer C3 right now.
Twin Arrows LV1 costs 15 sp and has 151 attack value
Lv5 brings the attack value to 320 but the SP cost to 27.
Is Lv5 a must?
Same with the Scout C3 skill:
17 SP for 332 attack value
37 SP for 631 attack value
Is the small increase in attack value into the formulae going to come out much bigger or is it a minor difference?
Its your c3 skill. You cant even spam it… max asap.
Yeah you either leave it a 0 or you max it. I highly recommand it
Twin Arrows has a 7 second cooldown with a 5 overheat.
Scout C3 Split Arrow has 0 second cooldown
Thats a lotta SP burn 
Anyway, I was just wondering what the actual difference is between the attack values for the SP spent.
Them do the math
Twin Arrows LV1 costs 15 sp and has 151 attack value (151 / 15 = 10,06 ~ damage per sp)
Lv5 brings the attack value to 320 but the SP cost to 27. (320 / 27 = 11,851 ~ damage per sp )
19,52 for the first scout
17,05 same for the max lvl.
So for scout the damage per sp is not good at lvl 5 but 37 sp is not that much, imo max both.