I see a lot of people talking about meta playstyles that they've witnessed in other games - for example, AOE groups, a certain class being the 'go-to' class for a certain critical role, the holy trinity synergy dynamic etc. They keep saying things like "If it becomes the best way to do things, it could get boring/overpowered/unfair".
Firstly, and the most important here - is let go of what you've seen in the past - we just don't know enough yet to be sure that 'the wizard will be a glass-cannon', or, 'the Cleric will be the best healer hands down', or 'the warrior will be the best single target tank' , etc etc.
Though unknown to us at this time, there will always end up being a best way to do things. Playstyles that will lend themselves to more efficient reward acquisition. That's just the nature of synergistic grouping games. Every choice the player makes should mean something, and this is one way that meaning becomes realised. Through increased risk, increased reward is usually a potential. Via minimizing redundacy of class abilities, and maximizing role effectiveness through intelligent group composition, extra efficiency can be obtained.
The opposite of this - almost any group composition is on par with any other - or any play style is on par with any other - then what's the point? It becomes flavorless and boring. A trophy for everyone is not the goal of this game, and it isn't any fun.
One way I think past developers have gone completely wrong in addressing this type of concern is making sweeping changes every few months that completely turns upside down the efficient playstyles and group dynamics - for example "flavor of the month class" is all of a sudden the top DPS spot while last month's "flavor" was nerfed into the ground. I really hope this doesn't occur as this game progresses. Small changes and adjustments - sure. But these should really be worked out in Beta prior to release. This game will likely require real time investment in getting to a level of proficiency that the player achieves, and turning around and making it all for nothing would really suck the wind out of many people's sails. Similarly with group dynamics - if there is a synergistic effect that is dominating the landscape - it should not be nerfed into the ground because the other group comps are complaining that they can't play 'the way they want' and be just as efficient as those others, over there. Those players made the right choices and picked who to group with to be most efficient. This is a big way that the Knights are separated from the Plebes in these types of games.
Ideally you would want a few different compositions of synergistic gameplay to be excelling - for example maybe there is a 'melee heavy' AOE group that rocks, and a 'caster heavy' AOE group that also rocks - but perhaps in different mob camp areas, due to those mob's abilities or the reality of the terrain. But almost always, one of those compositions or playstyles is going to dominate, even if only slightly. The trick is making these super efficient playstyles incompatible with 'face smash into keyboard' playstyles, and instead require individual class skill and understanding of synergy to achieve the given level of play.
This is often what makes the "best Tank" and "best Healer" class or the "best AOE" class be more desirable and in demand - players are hunting for one of a few different super-efficient meta playstyles and simply require those critical role classes. This is completely natural and should be the case in this type of game. So figure out how a given class fits into one of these meta playstyles and hunt for those groups - or better yet, form your own! This is a huge chunk of the enjoyment for this type of game for many! Enjoy it!