I'm happy for players to know all that stuff, at least after a round or two of combat. I tend not to reveal monster hp until they're in single digits, though: "1 hp left. Too bad..."
One issue I see with handing out extra monster information is that extremely good tactical players will shred encounters with it. I know some players that are extremely tactically minded and they'll do some things that would surprise even experienced DMs.
Once that starts happening, then the game starts becoming an arms race as the DM starts trying to challenge the players more via stronger encounters and the players start trying to eek out the very last ounce of optimization/tactical ability to win encounters faster. The game also can become an exercise in metagaming thinking.
Meh.
It's better to just keep the mystery in the encounter and then, even the very strong tactical players are playing a bit of a guessing game, at least part of the time. The DM can challenge them with reasonable encounters by mixing some things up a little, but without necessarily increasing the difficulty of the encounter.
And I find that more fun for those types of really tactically minded players than spoon feeding them the info. When they have to work for the knowledge throughout the encounter, then it feels better when they succeed. They actually overcame the challenge and figured it out on their own, as opposed to the DM giving them the answer.
DM: "That ones a Soldier and that ones a Lurker." (note: most DMs would do this via descriptive text, but it amounts to the same thing)
Good player: "Ok, let's take out the Lurker cause it'll do more damage and go down faster than the Soldier."
Rinse and repeat. Yawn. One might as well be playing Chess.
Even something as simple as DM: "That one's in single digit hit points" leads to the Striker players automatically ignoring that foe and anyone else, sometimes only the players with the PC with the absolutely worst attacks, taking it out. Meh. As a player, I would never ever ever ever ever want a DM telling me that a given foe is in single digit hit points. Ever. Does he want to hold my hand going to the bathroom as well???
Come on, make it interesting. Don't give me metagame info, hide that stuff from me, make some aspects of the encounter a bit of a mystery, and make it fun. Spoon feeding the info??? Yawn. Make it challenging, don't tell me everything I need to know so that my decisions are no brainers. I want to make my own decisions, I don't want the DM showing me the best way.
Note: My opinion of this extends into cross table talk as well. A little of it is inevitable, but if the better players start consistently giving advice to the less skilled players, I'll sometimes step in as DM and say "Let Joe play his own PC. You play yours.". Every player should have the ability to play their own PC without a lot of outside DM or other player hints. If the player is struggling, sure the DM should help out a little. But for most players, let them play their own PC their own way. They'll enjoy their own successes a lot more and when they do make mistakes, they'll learn from them.
In my opinion, the DM is making his game too easy if he hands out monster role information, single digit hit points, defenses, etc. And then most likely, he's upping the difficulty of the encounters in order to challenge his players. Meh. I prefer a more subtle DM who challenges me with misdirection than a DM who challenges me via brute force/monster levels, but at the same time tells me many metagaming things about his wonderful monsters that gives me hints on the best way to defeat them. zzzzzz
Hints should be for when the players are stuck in other aspects of the game, not for combat encounters. JMO.
