Picking a class
I guess I just limited myself to the ranger or mesmer…in any case, if you guys think I should try one of the classes above again because of something I might have missed, or maybe you see something that I might actually enjoy, don’t be afraid to mention it. I’m open to all ideas.
You can always make it harder for yourself, no matter which profession you are.
You shouldn’t dismiss Thieves as too overpowered. D/P is a very powerful weapon combo, but the others have their uses as well. Running about with D/P will in no way deal the most damage or make your PvE experience the easiest / most useful / fastest. So there’s much to brainstorm here and the benefit is that you can make your own rotations, thanks to Initiative. It’s very flexible and most fun!
Contrary to what you said, Mesmers are still “group-dependent”. Mesmers depend Heavily on their phantasms for damage. In a heavy AoE situation, you are pressed to deal damage effectively. Of course, you can minimize your illusions’ living time by using a shatter build, but that is more PvP-oriented.
I can’t believe I’m saying this, but why don’t you try a Warrior? In my books, Warriors are the most selfish profession of them all. I have also come up with a twist to make it enjoyable for myself, so it’s not too faceroll. Give me a poke, if you want tips 
Thief are strong damg prob one of the highest but Thief in pve all the way is a no for me cuz they are not easy as they look require skillful player to control and yes thief can bring down a champ all by it self but kinda selfish to me cuz pve is all about grp if you want endgame pve.
And for Guard what rune/sigil are you using atm ? cuz Guard is not at that bad in fact they can solo almost anything but you have to go deep into the class.
Ranger is kinda suit your playstye cuz they are jack of all trade easy to play easy to survive in open world due to pets but pet are useless or even a disaster if you don’t know what you are doing in grp play, run faster than mesmer but no challenge at all if you use a longbow…
Mesmer are good in both pvp and pve content but in pve they run a bit slower that might frustrating you but with the benefit they can bring to team they worth a try your clone can hold aggro pretty well tho and final mesmer/Guard are members of GWEN most wanted classes in dungeon.
So you can stick with guard and go deep into class gameplay or try something new by reroll a mesmer or just go with the easy way like ranger.
That’s all i can say for now it’s up to you to decide.