Within the Ring of Isengard, you'll find sewer pipes leading within the Tower and other zones. These are the instances of Isengard. Be ready to thwart the foul plans of the Wizard of Many Colours!
Fangorn's Edge (3-man)
The great fires that fuel Saruman's war-machine need fuel, and what better place to get it than the great trees of Fangorn? Stopping the fuel will weaken production.
In this instance, you get to see the huorns in action, killing the orcs trying to chop down the forest. The first boss is typical tank and spank, with the occasional summoned add. You'll want to try and keep the huorns at the edge of the battlefield alive as well. The 2nd battle is a 2-phase one. In the first, the ents come to root out the problem the orcs themselves, though they'll mistake you for one as well! As long as you don't draw ent-aggro and keep them alive, you'll be fine. Once the attacking orcs are down, 3 trolls come and lock onto one of the ents. Try to keep the ents alive while taking down the trolls (as long as your ents have a bunch of hp more than the trolls, you'll be fine).
Pits of Isengard (3-man)
Under Isengard, the Wizard Saruman is creating species of a foul nature. This instance features rescuable rohirrim that will fight at your side. The first boss is tank 'n spank and can knock people away or towards him, so be careful of those pits. On tier 2 he can summon adds. After this boss, there is a split (you can do one wing on tier 1 but both on tier 2). One leads down to the sludgepits which has another tank and spank boss and a nasty poison. The other side leads to the flame-pits. Make sure to rush the mobs together because whoever is too late is flung into the lava to his doom. This boss is tank and spank as well.
Dargnákh Unleashed (3-man)
The orcs have captured a troll, but have a hard time keeping him at bay. Once he escapes, all hell breaks loose and you have to drive the troll even madder (with ballistas and exploding barrels). Once outside, the boss can summon adds that heal him so make sure to kill them in time. Then it's time to kill Dargnákh himself. Make sure to stay behind him if you're not the tank. As you take him down, the ceiling will collapse.
The Foundry (6-man)
Saruman needs weapons and armor to equip his troops. While Isengard is completely turned into a warmachine, the foundry is a key location. This instance is among the more easy instances in the game.
The first boss puts up a damage-absorbing shield shortly after the fight has started. To dispel it, you need to pull him to one of the squares where, on pulling the corresponding lever, trash will fall on him to debuff him.
Now and then, lava will fill up a spot or steam will jet out of a grate, so try to avoid them. Just like one of the fights in the Grand Stairs instance, the boss can also call out a name where a damaging flame effect will appear.
The Tower of Orthanc (12-man raid)
Saruman has taken up the craft of ringforging. Even though his rings are lesser creations, it is still a good plan to take down the lieutenants he gave them to and then take the fight to the Wizard himself. This raid consists of 5 wings, requiring the first 4 completed before you can access the last. At the start you come inside a lobby of sorts (in the ring of Isengard) where the group can choose out of a few doorways leading to the different side-wings.
Ring of Fire and Frost
This one consists of a dual-boss fight. Attacking a boss gives a debuff to attacks from the other. On occasion, they'll summon grims that give further buffs/debuffs.
Ring of Acid
This boss will summon adds that have to be taken down. After a while, the room starts filling with acid which requires running around and jumping to avoid the pools. Once the acid is gone, attack the boss.
Ring of Lightning
Basic tank and spank. The boss will build charge and unleash it at times. As long as everyone but the tank is gone when this happens, you'll be fine.
Ring of Shadow
This wing has basic tank and spank. On occasion, the boss will summon aoe effects. One damaging one and one that only damages if you move. Therefore, the strategy usually is for only the tank to move.
A fight featuring 6 different Sarumans. Just keep killing the elemental Sarumans as each phase goes by. By using the rings from the other wings, you'll be able to defeat him.
Despite the high price, this is pretty much required at cap, seeing as this is almost the entirety of end-game. This might change with RoR but for now it stands.
The instances are fun to run, having some unique tactics. The 3-mans and foundry are currently run a lot, because the rewards are good (and in the case of Foundry ridiculously high).
The environments are varied and interesting, although some (especially in the raid) can be a little dark.
In the end, whether to get this or not depends on how close you are to the current cap.
I'd say to wait until you're 75 and then buy this (no reason to before that really), as RoR is coming in October, which might change the usefulness of this.