Can't say much about other classes, since I haven't played much, but I'll say a bit about the knight class (even though you scrapped it).
I disagree on what you think, knights aren't only tanks capable of sacrifice.
Yeah, they really are tanky, that's their main point, but that isn't their only usefulness. Aside from the tankiness, knights (especially crossbow) still have good damage outputs, so they are a really good class for solo kind of gameplay.
And this doesn't only mean actual soloing, it also means being able to do something on your own in group based instances.
Unlike some other classes which are completely dependant on their team (cleric/mage/bourg/arti and some kind of champs) to cooperate with them, a knight can do quite a bit on his own, and can fill a standalone warrior role.
This is quite useful in games where your team is a bit lacking (aka they suck), that you're still able to do somewhat well on your own.
For pvm, the knight is still very useful, especially when it comes to farming bosses. Thanks to shield reflect, your damage output in 1v1 situations is really high, and with your tank nature you can easily take down kings without needing much support.