It's a little tricky because the structure changed part way through.
I'm not 100% sure on all this. It's been a while.
The first 2 classes were sorc and beast master.
Then Necro released with 1 week left in Kickstarter.
Then void Knight released about a month later.
Then we completely restructured how we were doing things and we released mage, spellblade, lich, primalist, druid, Knight and paladin. This is when the first class wheel was introduced.
Then we split the wheel again and added shaman, sentinel and forge guard. (Removing Knight)
Next came rogue, marksman and blade dancer.
Then runemaster
And now warlock and falconer.
Biggest thing I'm not sure of is when Knight changed to sentinel.