In case missed and has not been added/fixed:

• 
  @Molkree: Can't replicate this, marking fixed for now as someone probably did it before.

• Learn to Ride quests
  
  
  @Molkree: This is really weird, these quests are in ATT for years, I double checked all of them now. I will create new char and try to recreate this, might be some error in reporting? Yes, looks like a bug with DisablePartySync tag, see my comment below.

• 
  @Molkree: Fixed in b1aaa48.

• Silithus Wound Missing
  Horde: Missing Waypoints (Silithus, The Wound)
  50053 Lazy Prospectors! 81 65.9 54.7
  50358 Desert Research 81 65.9 54.7
  50232 Twilight Survivor 81 65.9 54.7
  50052 No Spies Allowed 81 66.9 56.5
  50230 The Source of Power 81 66.9 56.5
  50231 Larvae By The Dozen 81 66.9 56.5
  50360 Khadgar's Request 81 65.9 54.7
  50055 The Speaker's Perspective 81 66.4 56.8
  50364 The Blood of Azeroth 81 42.5 44.2
  @Molkree: All these quests are in ATT for 2+ years, marking as fixed.

• Killing Ogmot the Mad triggered Quest #50225
  @Molkree: Fixed in 40798b7.

• 
  @Molkree: Added in eb76e24.

• 
  Added in 6186d71.

Okay, there is some bug in ATT logic concerning those "Learn to Ride" quests.
I have levelled dwarf and got similar results:

Here 32662 is a Dwarf quest, 32672 is an Undead quest.
It seems that ATT thinks that only 1 (2 really) quest is in DB, for the race you are currently on. For example here is what I see on human:

But at the same time Dwarf quest looks like it's not in ATT DB if you are on human:

At the same time Undead quest is always visible, and I suspect it's because it's the only one without ["DisablePartySync"] = true, in source.
I tested it by removing this tag on 32662 Dwarf quest and it became "added" to ATT on my human so I call it a bug with DisablePartySync and summon @ImUnicke!

This Learn to Ride issue may be fixed as a result of (7a05d16)? I forgot to check these quests specifically after making that change.

Yes, this is fixed.