I wouldn't necessarily say they need to deal more damage, but perhaps have abilities that enhance their performance and function. For example, Red Death could be improved by adding on to its Exotic perk the ability to increase damage or rate of fire when critically wounded, or simply adding Headseeker as an intrinsic perk like they did for No Time To Explain. Another one that could use an enhancement or overhaul is the ATS/8 Arachnid. Maybe instead of increasing the Zoom of Golden Gun, it could give it the ability to chain explosions with Combustion kills. Monte Carlo could use an improvement as well. Maybe add, as a secondary perk, an ability where melee kills refill the magazine, and increase its damage for a short time. Just little improvements here and there that play into the Exotic's overall theme, or is more suitable based on the Exotic's design, is all that is needed.