DDOCast spent a few minutes of this week's episode brainstorming about when and how the Dungeons and Dragons Druid class might arrive in DDO. The challenges with this class exemplify some of the issues that all games face when adding new classes.
The Mind is Mightier Than The Microprocessor
As nearly as I can tell, the big issue is that the class would require two major game mechanic systems that currently do not exist in the game. In addition to spell-casting, Dungeons and Dragons Druids have the ability to shapeshift into just about anything (animals, plant creatures, elementals). On top of that, Druids can tame dozens of creatures as animal companions, who can advance into sentient, intelligent beings that can then take a character class and gain class levels as if they were a free-standing character.
In a pen and paper RPG, these mechanics work because the game is being run by a living, hopefully intelligent Dungeon Master who can make a rational decision about what exactly happens if the player turns into a Fire Elemental while fighting Ragnaros (or whatever). Unfortunately, a computer game needs to be told in advance what to do about every possible situation, which requires a far more limited stable of options.
Working within the system
DDO's most recent new class, the Favored Soul, is also a divine spellcaster. However, unlike the Druid, the Favored Soul is effectively a Sorceror with different numbers plugged into some stats and a different spell list. The class has some unique quirks, but none of these required new game systems to implement. My guess is that the length of the wait for the DDO Druid will depend heavily on how much Turbine is willing to compromise on the class features (and how much compromise is possible before the class becomes nigh indistinguishable from its existing counterparts).
SOE and Blizzard have been able to implement shape-changing Druids in Norrath and Azeroth because they own the respective lores; if they say that the local Druids only know 3-4 forms, then that's all they know, and that's a reasonable number to implement. Turbine has previously implemented some limitations on spells that are not limited in the pen and paper game; for example, the "summon monster" and "summon nature's ally" spells can summon any creature of an appropriate power level in the pen and paper game, but are limited to a single type of creature in DDO. Even so, shapeshifting raises all kinds of complicated questions, especially when paired with other classes. This level of effort is not feasible for a single class - if they really wanted to do this, they could also implement self-shape-shifting for arcane casters to gain more milage out of their work on the backend, but that would remain a major effort.
The animal companion system seems more promising. DDO has NPC hirelings, who take up a slot in your party and can fill some rudimentary party tasks. It also has uncontrolled NPC pets from a variety of spells, and a recent game update put significant work into fleshing out undead pets for the Necromancy-inclined Wizards. In principle, these efforts might lay the groundwork for a more advanced pet system, though they're still a far cry from what longtime players might be expecting.
When to add classes?
The real challenge when adding one or more new classes to an existing MMO is determining how much effort it is feasible to spend on a single class. If you look at, say, WoW, Death Knights entered the game with a variety of new ideas (no single tanking tree, pets and heals and damage, several new types of resources) and have had to change to behave more like normal classes in the long run for the sake of balance.
However, if you do too little, there's no reason for players to be excited about new classes. In that case, you're just adding work for the class design team, who will need to devise a niche for the new guys for no good reason. The question is when the tradeoffs involved become worth the effort.
Will DDO Druids that look like Priests with slightly more robust pets and slight variations in their spell list make the cut? Time will tell for Turbine and Stormreach.