Maybe take a queue from tower defense games and have two ranges? First range would be the targeting range; how close the unit to its (or merely a) target to be to actually fire. The first unit in the "chain lightning" would be to that unit. The second range would be how far the "chain lightning" can reach when hitting additional units. The idea would be that the first range (the targeting range) < second range (the range that the "chained hits" can spread to). The idea is that as soon as a unit enters the targeting range, there are probably lots of other ships already in the "AOE" range ready to be hit as well. This would, in effect, "encourage" waiting to hit more units.
If (not sure about this) the current AOE range is fine, then only the "targeting" range would need to go down, but the current "AOE" range can stay. Not that targeting range matters as much for mobile major electric sources, as they tend to "bum rush" their targets as if they were melee units anyways.
The max DPS may (not sure yet) need to go down with this change, but the idea is that this could (possibly drastically) improve average DPS, possibly making it worth it. This is not intended to replace the other changes being proposed (more HP, higher ROF same DPS), but rather be something in addition to it.