The FPS still dip when there's a lot going on even on a strong machine, but deleting the shadercache.cooked in your live folder before logging in can help with random FPS drops.
Grand Warlord Arodel, Gryphon Heart
<Serenity>
AD MagDK, *2014, PC-EU | 49k+ achievement points
Sadly it's still an issue, and after playing for more than an hour you'll notice frame rate takes a nosedive in cities and other intensive locations. I have no idea what causes it, but I've noticed it gets worse faster if you travel around a few different zones, rather than stay questing in a single zone. Presumably it's not unloading assets properly.
It's an "easy" fix by restarting the game though, compared to so many other issues ESO has right now like lag and skill delay. So I don't think they'll be looking into this anytime soon, if ever.