You can't switch and interchange accessories at all?
Also, in terms of Auric tier alone, Melee has 2, Ranged has 2, Magic has 2, Summoner has 1 (that one's fair), and the Celestus can be used by any class, as it's classless.
On the subject of strategies... tell me there isn't a single boss in all of Terraria, mod or not, that has no reliance on a single kind of strategy used in order to best deal with it. Literally no boss in the entire game has a single, generalistically widely-used strategy in the ENTIRE game.
Eye of Cthulhu: run in a straight line. Dashes will never hit you, especially in Expert.
Eater of Worlds: use a melee/piercing/exploding weapon. In Expert, try to avoid staying still when it shoots vile spit.
Brain of Cthulhu: watch for it's teleports, and stay away from large clusters of Creepers. In Expert, it genuinely isn't that different, as only one brain has a health bar.
Skeletron: Big platform is preferable. Run back and forth, and jump over hands. In Expert, don't stay at one point of elevation in order to dodge skulls when he starts shooting them.
Queen Bee: several layers of platforms is best. Switch between them when she dashes. Get an exploding or melee weapon in order to deal with bees. spike balls also work to place on platforms to trick her into taking damage with each dash.
Wall of Flesh: big block platform across all of the underworld. run and shoot.
You see my point here, surely. But at the exact same time, you don't really have to do these things.
I've fought the wall before without a bridge. I've almost entirely abandoned the platform arena with Queen Bee, only using them to support like, heart lamps and campfires. With the Eye of Cthulhu, I tend to try and stay in one area so that it becomes a little more challenging... I don't like the fight with that one general method, it gets boring, as you say.
There are other examples of bosses that have been fought in ways people don't USUALLY do. Take Yrimir's Expert Moon Lord fight (at least the first one, I do not know if he's done it again.) He, instead of doing what a lot of people do end up doing for that fight, which is fighting the boss by only flying around and using the Rod or fast wings for the phantasmal laser, opted for staying on the ground for almost the entire first phase, using a small setup with a shield of blocks to avoid damage from the laser entirely. On Phase 2, he tries to outpace the eyes.
And in terms of Calamity bosses, take Leviathan's challenge with the Devourer of Gods, Cosmic Kunai only:
The tactics he uses here aren't tactics you can't use with other classes, with other weapons. I'd go as far to say that you can use these unconventional methods to deal even more damage to it than if you did some other way.
There is no one true way to deal with any boss in Terraria, or the rest of the game. I've utilized the methods Leviathan uses against the Devourer in my own fights, and it'd proven itself to be rather effective. Not only that, but it's made the fight much more thrilling and fun, as I have to dedicate a rather large amount of concentration in getting it
right.