All players should now be available.
This year's players do not have any factoring for all-defense, so once those are announced that set of players may increase in defensive rating (including Howard).
The major significance in the new defensive ratings is the removal of defensive rebounding from consideration. It's now based only on Steal%, Block%, Fouls, and Team Defensive FG%. The All-Defense awards basically just provide a rating "floor", so for example a player named to the 1st team can't have a rating below 90 for that season. As always, no system for defense is going to be perfect due to the lack of stats, but hopefully these numbers better match your expectations.
Thanks for your patience and let me know if you see any issues.