This stuff happens on every MMO.
Elite parties get to do the most complicated stuff.
Back in Lineage 2 (yes, once again) parties of archers and nukers were always fighting for the first place, be it at PvP or raids.
If you were an assassin or a gladiator, you know, duelist classes, you were most likely ending up in a mixture of different non-elite classes.
When you choose a class, you are not just picking skills and fighting mechanics, but also your advantages.
Some classes have a lot of single-target hard CC or heavy damage.
Those are duelist.
Some classes have a lot of massive CC while not reaching a high degree of damage. Those are control crowd classes, like supports that harm the enemy instead of increasing the stats of your group.
Some of the best compositions to do difficult tasks includes:
60% of damage dealers (be it AoE or single target, depending on the objective)
20% of support classes.
20% of tanks.
Not saying that if you are not included into those classes you won’t ever fight there, but if a guild tries to do it, they’ll arrange their raiding group the best way possible.
If you are aiming to do elite raids, you can build that way.
If you want to be a duelist and have the edge on every 1v1 PvP, you can aim that way too.
It’s up to you.
It’s also a fact that most supports and tanks will always find a free spot for most of the elite activities.
As for me, i’ll try to be a mix in between of damage dealer with a tank, that way i’ll be able to defend myself and also have enough utility to survive, I won’t be that useful in a group, but that’s how I wanted it.
Still, it’ll be my first serious build, i might just fail and have to create a new character, but that’s okay, being able to fail horribly is also part of the fun.