It's not a waste of money to add an e-locker to the 8.0" rear end. If you've been wheeling it without blowing up your R&P, then your results wouldn't change by adding an elocker. The improvement will come when you correct the loose factory pinion/carrier bearing preload. That's where a lot of the slop in the 8" rear comes from.
If you're wheeling with 35's and rock crawling then sure, get an 8.2". If you can get an 8.2" for cheap, then absolutely, it's the stronger of the two axles. That said, there isn't some epidemic of exploding 8.0" rear ends from guys on 285's running down forest service roads.
These diffs have been around design-wise for over 20 years without a long history of issues. The problem that we're starting to see is guys wheeling more high-mileage GX's. The higher mileage equates to looser bearings, which equates to more slop and higher likelihood of failure. Set your diff up with the gear ratio you want and a solid pinion spacer and you'll be set for worry free driving for what 95% of what GX drivers will ever put their GX through.
I've had my hands on 8" thirds from vehicles with anywhere from 20k miles to 190k miles and I've never seen one that I couldn't rock the ring gear with my pinky. If those are going to fail, it's because theyre out of spec, bot because of deflection in the towers.
Sure, Dan broke an 8.0" with an ARB... pretty sure he was on 35's at the time though and doing some above average intensity wheeling. If that's your plan, get an 8.2. Or a diamond 9.5 or D60...
At the end of the day, adding a locker wont strengthen your axle. Maintaining it to factory specified preloads will ensure you get all the strength it has to offer though which is more than enough for the majority of GX owners.