You do not need even CLOSE to an i-7 for this game. My girlfriend has an i-5 7500, and I have an I-5 6600k, never dip below 60 FPS on ultra. You have to take into account your RAM too, 16GB preferred. I run a 1070 and she runs a 760. Both PCs never dip below 60FPS in this game.
I have three systems. R7 1700 + rx480 4gb, r7 1800x + fury x, and i7 6700k + rx 480 8gb.
I've only tried eso on #2 and #3 ... They run about the same but unfortunately ESO just runs maybe 2-5fps better on the system with the highest IPC and Single core perf (the 6700k). I have only played about an hour on my 1800x and didn't try trials or zergs so if I do ill update this reply.
I hate being brutally honest because I'd never go back to my skylake build... I love this frickin fury Ryzen machine.
Most multi-threaded games are done with less than 4 threads. There is only so much that you can actually do at a single instant in a game.
Best bang for your buck for games is an i5. For multitasking (YouTube, game, teamspeak, random app) an i7 will bring some performance gains.
Apps all have different preferences on what is important performance wise, but you will not find any modern game on one core. Not any non-indie game anyway.
Given the new field AMD is fielding, I would suggest giving it a shot, unless Intel announces 8000 series (or whatever they call it) for the new factor.
*if anything I say makes no sense, I am frantically typing on a small phone with my second drink.
CPU wont matter from an i5 to an i7, ESO max's out one core and wont utilize the rest of them. i would not base a purchase of computer parts on this game,better to find something else to future proof your set up