The factory Ecopia's were/are crap! plain and simple. Like most mfgs. Nissan has enough buying clout to tell
the mfgs. what they will pay for a particular tire. It has to pass safety tests and preferably last at least a year, other than that Nissan doesn't really care
It's a win win to have a OEM tire wear out very quickly, for all(except the consumer)
When the tires wear out there is a chance you might go back to the dealer(dealer/Nissan/mfg. makes more money) or if you purchase your tires somewhere else, mfg. makes more money. Of course it could backfire if you the consumer get it in your mind that Ecopia's or Bridgestone in general are crap and decide to not buy Bridgestone's in the future but there's always new cars being mfgd. Note the aftermarket Ecopia+'s sold by bigbox retailers such as Costco are MUCH better than the OEM crap they put on the Leafs. My OEM Ecopia's didn't make 10k before showing pretty bad signs of wear, by 20k there were areas on the tires(mostly outer edges) that had no tread left
I've got 10k on my new Ecopia+'s with nary a sign of wear. The new tires also have a treadwear rating of almost double the OEMs. Note I'm also running the new tires at 44psi compared to Nissans suggestion of 38psi, something I'd suggest for almost everyone concerned about wear, particularly on the edges of the tires. 38psi is really too low, might give you a softer ride and maybe a bit more traction but really bad for wear.
Oh to answer your question more direct, get Ecopia+'s, very good LRR, low cost and all around good value for the money. If you want to spend a bit more for a longer wearing tire but slightly worse LRR I'd suggest Micheline Defender tires. I'd have really gotten those but at the time I needed tires they were over $100 more(for the set of 4) than the Ecopia+'s. If you hit the sales on the other cycle(Bridgestone's not on sale but Micheline's are) they might be within $10 of each other and which point I'd personally get the Micheline's.