D3 usually make the new character releases available in heroic the following season, as someone else posted. However, it might not be done right at the very start/first day of new season. You should check the “?” icon to confirm that your desired character has been added to the draw.
For example, the current season started at 8 pm est on a Thursday, but the new antman/thing covers were not added to the heroic draw at that time.
The Antman/Thing situation is why I asked. Heroic (?) has been known to be faulty.
Anyway, had no desire to wait 2+ more weeks, so opened my 12 tokens & 10-pack. Got an X-Force yellow, a Doc Ock Green and a Collosus Yellow I could still use, 3 golds I couldn’t and a bunch of two’s. Wasn’t getting that Jean with those pulls anyway.