Molten Core class sets you just go into Molten Core and smack the bosses around until they give you what you want. It will likely take a great many runs because they hadn’t come up with the token idea yet then.
How you get PvP season armor varies from season to season. You’re best off searching Wowhead for a piece from the season you want and work it out from there. For example, season 1 seems to be available from a goblin in Area 52 in Netherstorm for Marks of Honor, or alternatively from trading in tier 4 tokens on Isle of Quel’Danas.