Klandicar has Four AOE's to mindful of, two of which will be blocked by most of your raid force if you do this fight correctly. Chaos Storm II and III MUST be blocked if you do not have MT level hp. So plan your groups accordingly to block these AOEs. Your MT should have enough blocks and saves to handle all of the AOE's. Storm II and III hit back to back so you must time your group blockers accordingly to cover both AOE's. Four Druids can handle this easily with Tortoise Shell but remember to have them cancel it after Storm III hits so the recast is ready for the next round.
There will be an add that pops. You must DPS this add below 50% before Klandicar casts his Curse of Chaos ability. Reason being is that this add will spawn a bubble that blocks Curse of Chaos. You must be in the bubble for during that casting for most of the raid to survive.
So, you need to dps the add down low enough to get into the bubble for the Curse of Chaos AOE and then kill it almost right away when the Curse of Chaos aoe goes off and get ready for the next add that will pop soon after. You can't get backed up on getting those adds low enough because eventually Curse of Chaos will catch up to you.
30% health or so should work for most raids depending on your dps setup.
This fight is not very tricky in principle. This fight is all about timing your DPS and your AOE blocks to survive the fight.