The Viper MKIV has weaker shields than its MKIII counterpart in exchange for a much tougher hull, so losing shields quicker on the MKIV is normal. It's not usually anything to worry about as the MKIV's hull was designed for tanking and can sustain more damage than the MKIII, which should give you enough time to reposition yourself and/or flee to allow your shields to recharge. That said, you're running underclassed shields that may be contributing to the problem. You should try equipping 4A instead of 3A for some extra shield strength.

And maybe throw in some Hull Reinforcement Packages if you haven't already.
EDIT: Shield Boosters are also an option, but due to the MKIV's limited utility slots, I wouldn't bother. The shields will still go down anyway and the hull is strong enough to take hits. Repair costs shouldn't be a problem, either.
I haven't used shield cells much since they were rebalanced, so I'm afraid I won't be able to be of much help with those. You could equip one if you feel the need to, but take care to watch your heat management as deploying one will raise your ship's temperature dramatically during use. It used to be that you could spam them without any consequences, but now with the power and heat management issues, you have to be a little more judicious about their use. Personally, I haven't needed to use shield cells on the MKIV as you'll have more than enough hull strength to either escape or outlast the enemy most of the time.
The Viper MKIV is a great little ship, though! Enjoy it.