The problem is simple but fairly difficult to narrow down to one simple design issue. In my opinion, the flaw is around the trait tree. Yes some traits are broken, some fairly useless and others simply are in the wrong tree and cannot be used in an effective build. The solution I’ll present deals with this, but we need to setup some ground work first.
A larger issue exists right now, and that’s the design plan for future expansions. While comments by developers have all by eliminated the potential for new “tiers of gear”, they did not (even explicitly mentioned) that this did not eliminate the potential for new levels of gear to come out (e.g, level 90 exotics/ascended/etc). Take a look at the stats system right now. It is possible to stack to over 90% critical chance rating when taking into account all potential avenues for stats (food, etc). If one simply adds another 10 levels AND adds another 100 points to the trait trees (pretty sure all classes have access to crit via trait points) what your left with is a character that with level 90 gear could easily exceed 100% crit chance rating.
Clearly this is a potential problem, not only for balance reasons but for general game enjoyment. Horizontal game progression aside, the current trait and itemization system will eventually make it all but impossible for you to continue introducing new gear and/or levels to the game play experience. Other games have introduced rating systems, in which an effective % level is attained after adding up all of the rating for a particular stat and diving it by the level to achieve some effective number. This helps minimize the damage new levels can introduce to the game play. It is one potential solution.
If one assumes the previous solution, it introduces another flaw into the current trait tree system. To remain effective at level 90, assuming a new “rating system for stats”, you would be forced to scale up the award of stat ratings by placing points into a trait tree to make it worthwhile for a max level character. This in turn would devalue the impact of putting 10 points (or 15, or 25) into a tree and force players into specific builds that maximized full points to trees to be effective for end game pve, pvp, or wvw. This cascading requirement to max out a trait tree leads to a homogenization of builds popularized by characters and ultimately leads to cookie-cutter builds that players are forced into. The current design would effectively lead to an elimination of choice for the player (ooincidently this is the problem WoW faced and ultimately turned it into a, 7-choices per character, game). Clearly not the freedom the developers of such an open character building history ala Guild Wars 1 want for their player base.
Solution? Remove ability stats from the trait tree and re-allocate them to gear itemization instead. The ultimate decision of what stat’s and type of character I want to play rests into your already effective gear-customization system.
The next area of concern is the unfortunate state of traits in this game. Many traits clearly were designed in a time when a particular utility skill set or “build” was effective. Over time the build has ceased to be viable, and the traits remain. For example, early in development Ranger spirit pet builds were deemed effective, but since then the builds and its subsequent talents were made all but useless (via nerfs) and are now rarely used (from my conversations with several dozen rangers). Similar examples exist within every class, go take a look at some trait guides for the different classes and dozens of traits go unused. Clearly what needs to happen here is a different approach to class and trait design.
In Guild Wars 1 players enjoyed the ability to swap out their utility skills in all of their entirety. Reconnect with your previous fans and institute a similar policy with your trait system. I propose a tiered trait system that removes prerequisites altogether. It would look and function something like this (Ranger used as an example);
Trait Tier Grandmaster (3 Trait Slots)
Potential Choices: Remorseless, Signet of the Beastmaster, Trap Potency, Moment of Clarity, Empathic Bond, Bark Skin, Spirits Unbound, Evasive Purity (any XI or XII trait)
Trait Tier Master (4 Trait Slots)
Potential Choices: (any VI-X trait including the bonus sub traits)
Trait Tier Adept (6 Trait Slots)
Potential Choices: (any I-V trait including the bonus sub traits)
The revised system allows players to chose from a wider variety of traits, creating more inventive builds. As a result of greater choice, players will have more freedom in creating the character they want to play as. As a developer it will allow you to pick out talents that are currently placeholders of something better down the line. Traits that really have no place or usage can be removed and the effective perceived use of their characters class will increase.
The current system, and limited resources available to developers to spend on trait fixes and bugs really hampers players perceived perception on class builds. Most Necromancers will tell you the available builds to them they feel bring something to the table (hint: its not many and the two popular designs have names! conditionmancer and minionmancer). Introducing such a flexible trait system allows players to come up with new and inventive ways to build the character that matches their play style. It also keeps the choice component in your game when other games are removing it.
By implementing both of these changes, you permit yourself some breathing room in designing new content for future expansions. No longer will you need to worry about a stat system that adds little to an end game character approaching level 100 (power creep problems), but you can quietly deal with perceived useful builds that the population has been quietly hedging themselves into. In the end, you’ll have to deal with itemization and the feeling that the trait trees are mostly broken. This solution gives you some wiggle room into fixing and introducing new traits without requiring pesty trait tree prerequisites.
edit: Had a pretty nifty “Eureka” moment last night when tooling around in Far Cry 3. What about introducing traits to players based on achievements. Players could unlock traits that match their play style in game (corresponding to achievements). For example; running around the world is boring, but to a player who explores a single zone fully, you could unlock a 25% movement speed buff on the character they are playing on. I realize the potential downside being the current achievement system is account-wide and not character specific, but surely a workaround could exist. Unlocking traits via achievements would really mesh well with the exploration-depth of Guild Wars 2.