Bigger is better indeed for missions... But if you run too fast to battleships and L4s, you might actually find your new battleship is unable to do the missions. Support skills are important too. It's expected you'll train them up as you go. To use the maelstrom as example, the skills you really should have are:

• Engineering V
• Electronics IV
• Weapon Upgrade IV

T1 guns with T2 damage modules are better then T2 guns without damage modules, also helps with CPU)

• Energy System Operation IV
• Energy Management IV

Both skills essential to deal with the cap use of XL shield boosters.

• Shield Management IV
• Shield Operation IV
• Shield Upgrades IV
• Tactical Shield Manipulation IV

The 4 shield skills will allow you a good shield tank.

• Hull Upgrades V
• Mechanic V
• Repair Systems IV

Alternatively, for ships that are armor tanked.

• Energy Grid Upgrades IV

T2 Capacitor modules, essential

• Drones V
• Scout Drones Operation V

So you can field 5 scout drones, BS have problems killing frigates, this is strict minimum though, Drone Interfacing would be very useful to train up a bit, +20% damage per level. Dominix (or to a lesser degree Typhoon) pilots should train drones heavily since it's their main weapons.

• Jury Rigging III

So you can fit rigs, pretty much essential on a mission battleship. Large Capacitor Control Circuit I are the most common PVE rigs to boost capacitor recharge.