Okay, what I'm about to say isn't a new problem, it is old, and is something everybody has seen and experienced: I think caps are too vulnerable to masses of illums/lrm/assailants.
caps = expensive, not spammable
cap killers (illums, etc) = cheap (relatively speaking), spammable
You see the problem? Herds of relatively cheap spammable units vs. a couple expensive caps?
The problem is this. Caps are supposed to support the fleet. Or, if you are a "new school," cap-heavy kind of guy, fleet is supposed to support the caps. But under most circumstances, you simply can't put caps in the same grav well with a mass of illums and have them do anything but die. And if you can't put caps in the same grav well where the action is taking place, how are they supporting anything (or conversely, being supported by anything)?
I don't think caps should be immune from death by any means. I think caps should be counterable and killable. But I also believe they exist for a reason besides running around colonizing planets or rushing. They are supposed to be able to support a fleet in battle (or have a fleet support them, whichever you prefer). But they can't do that if they just die to a wall of illums or assailants or lrms.
Does someone want to tell me that the current balance between caps and masses of cap killers is fine? If so I will listen. Otherwise, I propose some mechanism to balance it out. Something like a "diminishing returns" on the attack of cap killers after you hit a certain number of them (i.e. all cap killers after 20 do 70% damage to caps, all after 30 do 50% damage to caps, etc). I mean, I don't really care what the mechanism is, there just needs to be something.