I know what 30 fighters and 30 bombers supported by 30 flak frigs can go. They can fall before my 60 fighters and 30 flak frigs. Bombers need at least a 1.5:1 ratio vs enemy fighters to be worthwhile, and when fleets start getting large the cost of getting to that ratio gets prohibitive. Just build some heavy cruisers to lay the smackdown on capital ships. Unless you're not Vasari you'll end up doing more damage that way anyhow.
The real problem with bombers is that the interceptors don't, by default, protect your bombers. They mindlessly chase the other guy's bombers. Sometimes that's what you want, but it depends on how you've built your fleet. Other times it's much better for the interceptors to ignore the enemy bombers and destroy other interceptors. This is especially true if your bombers are one of your fleets primary offensive weapons. However, there is no good way to do that. Focus firing your interceptors on enemy interceptors, even if you can do it during a huge battle (which you can't) works poorly for two reasons. 1) all your interceptors chase after one squadron of enemy interceptors at a time and 2) your interceptors will waste enormous amounts of time killing every last enemy interceptor in the focus fired squadron without moving on to far stronger and more dangerous squadrons.
This could be redressed with the ability to set targeting priorities for your units. If any of you have read my posts, you know this is someting I've kind of harped about for a while, but I don't want to miss an opportunity to get it in there.
Personally, given how hard it is to protect bombers, I prefer to fill my hangars with all fighters and instead of using bombers for offense, I use heavy cruisers with a few LRFs and light frigates to run interference for the HC's. I will occasionally use bombers only in a couple of circumstances. Sometimes I'll use a handful of them merely as sacrificial goats to draw the attention of enemy intercetpors, so my interceptors can hunt enemy bombers without having enemy interceptors snapping at their heels (because in the abscence of bombers to target, intercetpors will chase other interceptors). I will also occasionally use significant numbers of bombers as TEC in a long game. That's because a mid to high level Kol with lvl 3 flak burst and a lvl 6 Dunov working together can pretty quickly enforce total control of the sky. Once that's done, then I release my bombers to attack and without significant interceptor opposition, it's pretty much a massacre. Problem is, this strategy is dependent on a pair of relatively fragile cap ships, so even with those two caps I don't prefer this strategy; it's too easily unraveled.