Dragon fighting tactics?

When I've either run (DM) or fought (PC) dragons, it's always been mobility and AoOs on the dragon's side that have been key. Dragon's move is crazy good.

The last time (a TPK, BTW), the dragon simply hovered above the PCs, out of their reach, but within his. With his standard actions each round he'd buff himself with mirror image, blur, mage armor, etc. The dragon started by hovering over the archer.....until he was meat, then hovering over the mage, until he was meat,....etc.

So: What can the PCs do? Figure out a way to limit dragon mobility.

Again, is this the CR 11 or CR 14 dragon?

If you are really going for a tactical battle, drop teh CR down below the party's level and then player the dragon very smart. He will still be a very strong challenge, but hopefully the players could retreat if they truly needed to.

I have found anytime a monster can isolate party members his CR is much higher than is indicated. With the ability to pull players into the water, your dragon has this strong advantage.

I think some of you are overestimating this dragon.
An Adult Black Dragon is not gigantic, it's about the size of a horse. Size Large.
It isn't a genius, it's fairly bright and cunning (Int 12, Wis 13).
It's strong, but not overly so - it can fly with a 600-lb load, so with an Enlarge Person spell it can't carry you in flight.
It has a 10' reach only with its bite - which does 2d6+6, not a devastating amount to an 11th-level PC.
Its breath weapon does 12d4 (average 30), which an 11th-level caster can mostly negate with a 3rd-level Mass Resist Energy spell.
Its spellcasting ability is minimal and its SR will stop about 1/3 of spells from an 11th-level caster.
It has only natural healing ability. Hit-and-teleport tactics can wear it down if you can do more than 19 hp per day and take less damage than you can recover (and make the dragon use up wands, potions, and scrolls).
Most importantly, the PCs know what they're up against and the dragon does not. Who are these humans? Are they ordinary humans or are they legendary heroes? What kind of resistances do they have? This dragon can't scry. The PCs can.
An 11th-level paladin can easily hit on a charging smite (backed up by Bull's Strength, Greater Magic Weapon, and a boosted Inspire Courage), and with Spirited Charge it will hurt the dragon a lot. Use Fly on the mount (and on the paladin in case he's dismounted).

Now, that said, this party will be in trouble. No single-classed caster, so the SR will be tougher and some high-level spells will be unavailable. The rogue's sneak attack ability won't be that useful due to the dragon's blindsense. I don't know much about 3.5 psionics so I can't say how useful that will be.

Basically, Mass Resist Energy and Enlarge Person are good options to start with (even though it can't Snatch, it could try grapple-and-move). Lantern archons would be a good summons, as they can do guaranteed damage each round.

I don't know the details of Quicken Breath Weapon, but it sounds insane. If any feat is so good that every PC would take it, it's overpowered. QBW sounds (from its name) so good that every single dragon would take it. But, again, a 3rd-level spell and you negate most of this dragon's breath weapon (and it won't be able to tell that the spell is applied to all of the PCs until it's tried several breath weapon attacks).

hi please and thank you

Could you please tell me what the bard did?