Not even talking about waves - I was playing with low ship cap, and they've got 4.2 million hitpoints each at mark 2. The problem was that there'd be a couple of them getting released from incursions onto a planet, either from destroying the command station or a guard post or something, and five of those plus a small escort (to distract turrets and the like) will easily trash an entire planet. Even if you know they're there, a full cap of mk1 and mk2 fighters takes forever to kill even 1 (I know technically they're not supposed to be good against electric bombers, missile frigates are the "counter" triangle ship, but the missile frigates aren't really fast enough to respond to a random incursion before the 5 electric bombers have gibbed your entire planet).
Basically, the electric bombers were causing problems equivalent to if it were say, 10 bombers to 1 electric bomber of the same mark. I would NOT want to see 10 electric bombers show up on a planet I hadn't dropped heavy fortifications on. I eventually just gave up on that game because the combination of electric bombers and sentinel frigates being two AI bonus ships was making my life absolutely miserable.
I guess I should have realized though that 1 tractor beam can lock down that entire force (maybe, they may still do enough damage to just instagib the turret), it's just with the way I was trying to set up my defense I hadn't thought of that since tractor beam turrets tend to be expensive and energy intensive for what they actually do and how fast they actually die.
On the player side though (I tried out the new electric bombers after a couple game where the AI just randomly ended up with electric bombers over and over), I found that the electric bombers were very nicely balanced. They crank out a pile of damage, and are reasonably durable (keep them away from artillery guardians, fortresses, and ion cannons unless they have a nice escort), but they are well worth it on offense if you need a super-heavy bomber. They also combo well with transports since you have a total cap of 24 of them, which means you can dump them in a hurry to smack a command station and then turn around and run.
Overall, I like how they're balanced, but the AI just gets sheer numbers of them and that makes them extremely hard to deal with. Maybe increase the number of reinforcement points needed for the AI to deploy an electric bomber, to cut down on bomber spam? They still show up in reduced numbers, but those reduced numbers are still 10x more than they should be. If anything, they should be showing up something like twice as frequently as starships, since at normal cap they tend to have about half the hitpoints and damage of a similar mark bomber starship, and they about match fleet starships for hitpoints and do more damage than fleet starships (at least for light starship and flagship, I don't think that holds for Zenith or Spire starships).