My last graphics card test retains the Ultra preset, but increases resolution to 5760x1080 using three FHD displays. Naturally, lower-end hardware is hit particularly hard.
The Radeon R9 280 (formerly Radeon HD 7950 Boost) and GeForce GTX 760 are as low as I'd go to play across three displays using this game's top image quality features. Even then, you might want to drop the detail preset down to High.
To truly maintain frame rates in excess of 30 using the Ultra-High setting, you need a Radeon R9 280X or GeForce GTX 770.
The dual-GPU Radeon HD 7990 and GeForce GTX 690 don't appear to offer any performance advantage over their single-GPU counterparts, suggesting that The Elder Scrolls Online cannot yet take advantage of CrossFire or SLI. We even tried forcing CrossFire on without a profile, to no avail.
Our frame time variance numbers confirm the hypothesis about CrossFire and SLI, demonstrating consistently-high lag between frames rendered by the dual-GPU boards. In contrast, all of the single-GPU solutions fare well.