Are you hiding your Escort Carriers in the far corner? Remember that an SSD's reach is pretty impressive: between their sheer length and weapon ranges, it's usually enough to hit most ships--and destroy them, mind you, because the odds of successfully drawing all 138 weapon hardpoints away from the rather fragile fleet are so drastically small as to be impossible, unless you treat your carriers like ground troops you accidentally took with your fleet.
In short, some of the guns are inevitably going to find your ships, and then you're in trouble. This is why I advise bringing along some heavy guns: something has to bear the brunt of your fire, and it's probably not going to be even a Victory II. I do have to say you have one way of being efficient with pop space and money, but for heaven's sake, take a Star Destroyer with you. Or, better still, build three or four of those "squadrons" (in other words keep the proportion, but add more ships).