I'll just add that unless you're an incredibly seasoned multiboxer who understands the challenges that lie with multiboxing M+ encounters while playing multiple characters, I don't think playing five different classes with five different specs is going to work out all that well, and even then it's still very likely to be lackluster compared to the "proven" team comps. On paper, sure, spreading out your classes to cover a bunch of buffs and added utility sounds great, but, in practice, it's usually just a hindrance to micromanage everything during progression fights that require all of your attention.