Max hull, Max defense and lots of fixer profession members is one way to go. Basically be a turtle and make them spend gobs of energy.
Hate to say it, but you guys are in the sweet spot for base combat. There really isn't any effective way to keep a level 4 alive. Strongish legions can take you out solo, and little guys that are looking for something more than just badges will team up with other legions and go at you. Best bet is to make it to level 5, then you only have to worry about the really strong legions and alliances. The little guys won't be able to handle you anymore.
_________________Ranks 400+ Join us in exploring..

[20:40] Wredz: just hacked a massive extremely rich minting planet from someone.. thats the best planet i ever hacked
[20:43] DarthFlagitious: is it spearmint or peppermint?