I've run an elec/elec blaster longer than I've run scrappers. It was the second character that I ever created on live back at release and I never stopped playing him. Elec blast just feels light on damage compared to most other sets. The trade off is of limited use, at least on blasters. I've played a sapper elec/elec build for a long time. Yes you can use it, but other blasters are killing the mobs or the team has already moved on. With IOs other blasters are not at much threat from anything that you could fully drain. Elec Blast lacks multiple heavy single target blasts or ranged AoE attacks that it can use to leverage extra recharge into higher performing attack chains. I think only two tweaks would shore things up a lot in making Elec blast on the Blaster much more satisfying and without overpowering it.
1. Make Tesla Cage cause damage in addition to its hold, at least as much as Lightning Bolt. I think it could be made into a true tier 3 with a hold and that it wouldn't do anything to harm balance. But even tier 2 damage would help with low level attack chains, and high level overall damage dealing.
2. Make Voltaic Sentinel a real, controllable pet. It's damage isn't high, but if you could control what it was shooting at like a Mastermind minion it would become a lot more useful. Weak HP and its cast time would be worth dealing with for the extra damage. It would also make the pet unsuitable for tanking, and keep the agro on the blaster since it would easily out damage the pet. It would be a nice support pet for a blaster without adding anything drastically new. It would alter the IO type for the power, but it would offer a lot more in terms of game play.
Combine both of these changes and you would shore up the Elec/Elec blaster as a damage dealer, preserving the current play style, and at least in spirit staying within the cottage rule. If you try to redesign the endurance drain mechanic it would be more difficult and do nothing to help the damage of the blaster version, and no matter what the blaster's control will be much less than an actual control class. Blasters are for damage. Chaining attacks would help with AoE damage, but do nothing for single target.
Elec doesn't need more recharge, it doesn't have enough damage dealing attacks of sufficient strength in single target to get a good damage boost with that extra recharge. I don't think that the set needs an endurance boost either. Without a tier 3 attack, it can't stack multiple high recharge attacks to develop a higher end attack chain that other blast sets can.