Raiding challenge
Perhaps have a boss be immune to hard dps for 5-10s, so condis will only do, vice versa and other combinations to make it more engaging skill experience, just not numbers but a mechanics game! GL
I am not sure you understand what you are asking.
Most of your suggestions already exist in the raids.
the number of “required” classes is exactly zero.
There is only 1 class that uses primarily auto attacks,
By having a boss that requires a specific class, Engineer in your example, would go against the very basic idea of what GW2 was supposed to be about. ( not waiting around for hours on end for a healer, etc)
Every single class is Raid capable.
and in some cases there are more than one variant of said class that is raid capable.
so what is the problem again?
There is only 1 class that uses primarily auto attacks,
This.
Unless you are getting carried HARD by your raid group, 8 out of 9 classes won’t be running auto attack only (maybe 7 out of 9 if you count revenant as autoattack class as well, which they shouldn’t be).
Suggest: They bosses need to make it so people have use more then just autoattack to attain the highest dps otherwise most fights will remain this 1-4 class must haves, make the boss challenging and having people to think of different combinations/classes needed to do things or get past things. For example, have a boss that disables peoples healing ability/elite skills for certain amount of seconds..so in term people will have to think about what else they could use to compensate..which gives diversity in skills. Or make it so that a boss needs to have a engineer for a specific reason. Give a little more dynamic-ism to the fight for classes to brainstorm. Good luck and keep up the hard work.
I don’t see why it matters that some classes have autoattacks as one of their highest DPS skills. That means they get to bring more utility and are useful in other ways (e.g. stand your ground on guardian). The one exception I think is thief, where staff autoattack is better DPS than all other weapon skills and their best DPS build also includes two signets so they effectively have 1 utility slot. In general though I don’t see why max DPS rotations need to meet some level of complexity.
The reason there are must-have classes in the fight has nothing to do with raid design and everything to do with the way the classes are designed. Druid, Mesmer, Warrior will be used in any fight where you have to deal damage with your character (i.e. all of them) because they provide offensive buffs you cannot get anywhere else. Elementalist will be used in bulk for most fights because their damage is so high relative to other classes, unless there is a quirk of the fight that makes another class better (e.g. necros on matthias because of condi manipulation).
You could have the boss disable healing skills if you want, but it wouldn’t change the way people play because everyone is already trying to avoid damage as best they can.
There is already a boss that essentially forces you to bring an engineer (vale guardian). I do think it’s funny though that you say you want people to need to think of different combinations to get past the boss, but then suggest that a boss hard require a specific class.
The problem (if you see it as a problem) of “must have” classes in raids is much more easily solved by changing a few specific skills/traits than by making outlandish boss mechanics that require really specific stuff.