It's highly important since level 3 missions provide some buy DFO Gold of the best pay available in Eve Online for characters that like to solo, not to mention that it will take you a long time to gather the skills and resources needed to adventure on those perilous level 4 missions which will often enough require the help of another player. Battle-cruisers are a different breed.
Although the damage output will increase, it's nothing dramatic, not compared to the massive boost in tanking abilities.
I suggest you get tier 2 shield extenders, no less than five of them, the maximum number. Low Slots can be fitted with a ballistic control system for the extra punch and three shield power relays.
The shield recharge time will drop to unbelievably low times, boosting the natural recharge rate through the roof. Forget about shield hardeners or shield boosters because you don't need them with 15,000 shields and from 20 to 60 shield regeneration per second.
Shield regeneration is lower when you are at full capacity and raises accordingly once your shield hit points drop, with a maximum effect at around 35%.
As you kill your opponents, the overall damage per second done to your ship will decrease, along with an increase in regeneration. You will most of the time find yourself with half your shield up and enemies unable to damage you any further. Now that's a sight!