First of all what does best class season 6 mean FOR ME:

I will have to mainly play solo. As I want to be still able to compete vs players who have good group I want to clear high grifts really fast. I also want a class that is able to clear t10 rifts really fast. I played wiz and sader last season pretty much so I would prefer to play other classes. However remember that I still want to be able to farm lots of exp in grifts.

Thanks for your advice

my advice would be to pick a class you like to play

this is pre-season and like every season before s6 the best class will change throughout the season

every class will be able to clear t10 really fast

yeah but for example, sader and wiz can clear high 90s. Barb, monk, wd and dh are at 80+ on ptr.

I liked the playstyle ofr crusader in season 5 as it was quite simple to play and not something like buttons smashing (not good for me as i have injured elbow joints)

I will say that sader is still your best choice. LON bombardment for t10 is really fast, easy with not too much buttons smashing. Easy to run solo 80-85 with no kind of fishing (good XP). I've not try the new invoker, but people seem to run 90+.
The free set for sader is akkan in S6. You will be able to run t10 fast enough at the start with the phalanx, just loot or I've try a bombardment setup with akkan, belt of the trove and the weapon/shield set Norvald's Fervor with in-geom in cube, it's good enough to setup you real LON build or invoker, if you want to play that.

thanks for advice. I just did grift 85 with crusader first try. good gear but still room for improvemnt. What do you think about uliana monk? can it go 90+ too?

I have play in S3 the uliana build and I hated it, to much fishing, need map with alot of mob, need boss with add, etc. I don't know if they change for S6, but I think it's the same setup for the monk.

Uliana cant go to 90+

How do creusader and wizard perform after stacks getting limited to (cursader: 20 and wiz: 60)?

Is the Raekor/IK still dominating the solo barbs?

it is on ptr, only change is that you use raekors 6 /4 ik and forced movementspeed doesnt work anymore.