Elder Scrolls Online will have four player classes when it is released in April. Each class has three unique skill lines, and a fair amount of flexibility in how they can be built. Players in the beta release have had a chance to explore and test out the different classes, and from both official releases and the occasional beta leaker, we've learned a fair amount about what to expect from each class.
The flexibility of Elder Scrolls online classes means that each classes can be built to fill at least two, and sometimes more, roles in group combat. A DragonKnight, for instance, can do high DPS, tank, or handle support and buffs for the group. This means that unlike in many MMOs, where a certain amount of class balanced is forced by the need for play groups have at least one character for each role, in ESO, three Nightblades in a play group can each handle a different combat role, leaving no need for more than one or two other classes. This means that the game can be highly unbalanced in the number of characters in each class, and still have plenty of functional play groups, which is what may be happening in beta.
An ESO spokes person mentioned in a recent interview that so far the most popular Elder Scrolls online class is Nightblade. This flexible rogue can be built in several directions, from ambush specialist to close in fighter to magical support. Roles the Nightblade can fill include DPS, tank, support and (possibly) caster. Plus, they get lots of fun sneaking, stabbing, and stealing skills, always a perennial favorite.
The Nightblade class is usually played as a traditional rogue, in light armor, with bow and arrows or paired blades. ESO's customization options and flexibility allow a wide variety of builds, however, and a Nightblade tank can use heavy armor and still disappear from the battlefield when they feel like it. (Heavy armor makes it harder to use the stealth skills, but it's completely doable.
While it isn't official, DragonKnights appear to be the next most popular class, with its variety of build options and fighting focus making it another popular option. The DragonKnight skill lines include skills focused on dealing damage, absorbing damage and boosting healing, and supporting other players. It can easily be built as a straight up fighter, and with a little effort can make a respectable caster.
It's too early to say yet if the game's popularity will last past the end of the beta release. It's possible that when the full game comes out, focus will shit to Sorcerers or Templars. We may also see Elder Scrolls online classes expanding in the future, with new classes or new class skills, that will lead to a shift is play styles and popularity.
When that happens, we may see the Nightblade replaced by another class as the most popular, or perhaps not. Everyone loves a rogue, and Nightblades may remain the most ESO gold spend for as long as the game is played. Only time will tell.