Monsters, CR, and BaB

[Gunslinger]

Is there any pattern used to determining the BaB of monstors? I ask because I am going to run an adventure out of Dragon(my first time DMing) with a "Giant Ogre(it isn't actually giant sized, it's 14ft tall, that's just what its called)" at the end. This thing has 5 HD, 2 attacks(+12/+7), and does 2d6+6 as written (but I don't see how a large creature can wield a huge greatclub 1 handed, so unless I'm wrong it should actually be 2d6+9). It has a strenght of 23 and weapon focus, and 80 hit points. I know if it was a PC it shouldn't have 2 attacks with only 5 hit dice. This monster was given a CR rating of 5, but that seems a tad bit wrong. 4d6+18 damage per round seems like a whole lot for a CR5 monster. What CR should this thing actually be, and should it have 2 attacks?

 

[Crothian]

In the front of the MM (pg 13) it lists all the variations for the monsters by type. Giants have BAB of a cleric. Use the creatures HD instead of levels to determine what the BAB is. In this case it should be a 3. So, it should have one attack.

You are correct that the huge greatclub should be a two handed weapon making that 2d6+9 damage.

Given the info you list the attack should be at +10.

I'm curious how it has 80hp. The HD type should be d8. Average HPs for 5d8 is 22, so this thing would need to get 58hp off of con. Assuming toughness feat, it would need a con of 32 to make this happen (+11 con bonus times five levels equals fifty-five, plus three for toughness gives us our fifty-eight). So, unless the Constitution is a 32 or 33 and it has the toughness feat, the HP are wrong as well.

Now, this creatures is horrible placed together, what issue of Dragon did it come from? If it is reassembled correctly, then CR 5 seems about right.

 

[Dr. Zoom]

The BAB as you listed it would be +6/+1 (12-6 str +1 wf -1 large). 5 HD for a giant is BAB +3, same as a 5th level cleric. So this ogre must have some class levels, probably 3 levels of barbarian with those hit points. Don't forget to let him rage 1/day and give him another feat.

 

[Gunslinger]

I'm sorry, I read it wrong. It actually has 8 HD, listed as 8d8+48 with a total HP of 80, but with only has 55 remaining (because it's been hit with some arrows). I don't know where the +48 came from though, because it's con is 19 and it doesn't have toughness. I guess the BAB is right, but doing an average of 32 damage per round(4d6=14+18) seems downright nasty for it's CR. Even a fighter(5th level) with a con of 18 and maxed out HP could barely last 2 rounds one on one.

Edit-It's from Dungeon isssue 83, the "Iriandel" adventure.