Alright, another round of responses.
Again, if you are one of my player's, I don't suggest reading.
Reaper:
2) The blue doesn't have bull's strength. I could have used entropic shield and protection from good (but that would assume the dragon knew they were good). So I could have turned on entropic shield, but that's just one more spell I can use to heal the dragon as he turns around to finish off the party.
3) Not sure what the point is here. I still say a dragon's attack is better than just about any second level spell I can choose to have him cast during combat.
4) The party knew it was a blue, it has lit breath, and that's it. The party hasn't seen it cast spells.
5) No minions in this instance. The dragon is new to the area and hasn't gone about building his forces (so the possibility is still open).
6) I generated a random hoard as per the rules. I'm playing a relatively low magic game, so many of the NPCs in the world do not have a great deal of magic. The party does not have an abundance of magic items/armament, so the randomly generated treasure was fine. If he had anything worthwhile to use, he would have.
7) The party has the location of the den (assignment is to retreive a few gems from it and if they want to kill the dragon they are welcome to try). They have not reached the den yet and they will likely retreat at the next opportunity.
9) He has ventriloquism, he can use it later.
12) I'll work on it. The full attack action of the blue dragon is quite formidable though, especially considering his damage mostly came from ranged attacks. He can either fly-by, strike only once, then go into the air again or do a full round attack routine. Either results in roughly the same amount of damage for the dragon, but the full attack action results in more damage to his foes.
13) If the party wasn't hiding under the rock ledge, then that would be effective. Yes, it would be very dangerous to attack the dragon again, considering he now has considerable knowledge of what the party can do.
Common
The people of my campaign world have not had contact with dragons in a couple generations. I don't see anything wrong with the dragons shunning or flat out killing humans (or elves or others) to protect their territory to the north. Now that the dragon has met some formidable humans who do speak common (and draconic), he'll be more inclined to learn the language.
Has this dragon seen humanoids before? A couple dozen in the last few months. What has he been doing for 149 years? Living in the north among a slowly growing population of dragons. Dragons are territorial, and so this one decided to leave the increasingly cramped territory for a new area.
This looks like a textbook case of the DM looking at the MM entry and just playing the dragon as a set of stats.
I thought that's what we in B.A.D.D. were against?
I thought BADD was against "disposable dragons?" I did RP mine with a background in mind, had it kill a party member in combat, and escape to fight another day. I'm sorry if you don't like the background or find him unreasonable for not speaking Common, but I think he did quite well given the circumstances. Was I light on the party? I don't think so. Not only did a character die, they have to contend with the dragon again, a dragon who knows the tactics used against it the first time.