You start with the title "best class" then ask for our opinion on what our favorite is. FYI, when someone states what their favorite whatever is it's not going to be an opinion, ever. It's going to be a fact.
Also,just to answer the topic, the best class is study hall.
The best class combo in the game is always the one your playing. Took me 2 days of testing beforeI picked the combo I enjoy which is Bard/Ranger. My advice, your paying for the game so pick something you love. Don't pick something based on another gamers exp.
In this case...you're asking for two separate things. You first ask for "What is best?" and then "What is favorite?" The quality "Best" can probably be objectively deduced, but favorite is a matter of opinion.
I only mention this difference because you at least seem to be asking these two separate questions as if they were the same thing.
I read nothing about the classes in this game before playing. I gravitated to the Warrior role, and just by reading abilities and checking up on how they combine on the Wiki, ended up with Rift/Para/Champ. Now to find out it was considered an OP build in beta, I can tell you I absolutely OBLITERATE mobs with little to no risk.
It's almost stupid how powerful this combo is.
Oh and Rift's spammable ranged attack that combines with the attack increasing early Paragon skill is ridiculously OP at early levels. I just stand at range with 3 attack points, hit the attack increase (iron something), spam the range attack over and over again. Dead mob. Next.
I'm not totally loving this game, because right from the onset it's very cookie-cuttery with clearly OP'd combinations. --- "Therein is your error, smoke not the bowl, smoke the contents." - Greendrakkon | A kid complaining he wasn't high after "smoking 2 bowls."