Screenshots for iPhone 4/5/6/6+/iPad I must attend to edit screenshots for an application, available on iPhone and iPad in 14 different languages.
Each screenshot contains a text explaining the screen in all 14 languages.
As each iPhone requires a different image size on iTunes Connect, so I have to edit: 14 x 5 x 5 screenshots different resolutions. This makes a total of 350 screenshots for iTunes Connect, just for one app.

My question is: there's there a simpler solution, less tedious than having to edit each screen in each size in Photoshop?
Thank You
There are solutions to automating editing and generation of App Store screenshots. Whether you find them 'simpler' depends a bit on what tools you're comfortable using:

Editing existing screenshots?
If you're adding frames and title texts, you can automate this with FrameIt (if you are comfortable working in the command line).
Other generic image editing problems: Use Adobe Photoshop and make friends with the Actions palette.

Generating new screenshots?
Automate generating new screenshots across devices and languages with Snapshot, this relies on learning a bit of the Instruments app and specifically UI Automation, and some command line fiddling.

If I were to recommend, I would work through automating generating new screenshots rather than fiddle with editing existing screenshots. This might have a harder learning curve, but once done you should save a lot of time when preparing screenshots for future versions of the app.

Snapshot and FrameIt are both part of Fastlane toolset for automating the App Store submission process.