This isn't meant as a discouragement to people like Kevin, it's just a general information thing. I agree with Holly. I much rather would have taken my mage the other night, but seeing that we didn't have any other priests for shackles (not slackers... oops, i'll L2read) it made it a hard choice.
But anyway, I only speak towards the casters here as I haven't played melee, ranged, or tank classes in Kara. When choosing your gear, +spell damage is great (and a required part) but you also need to be worrying about +Stam, +Int, +Spell Hit gear.
+Spell Hit: I noticed that I was getting a LOT of resists the other night because Imcu's damage gear doesn't have it. Nothing lowers your damage output faster than a resist.
+Stam: If you don't have enough HP, you won't last thru a charge (even Durruck has problems on certain mobs)
+Int: Some of the boss fights last 5-8 minutes...maybe longer. Can you find sources of mana for that long?
+Spell Damage: Base damage isn't enough. The more +dmg everyone has, the shorter the fight. Then +Int becomes less of an issue.
From the standpoint of a player that has 9 toons on the server, and 5 of them are currently active... make sure you're good at all the roles you need to fill with whatever toon you bring. I brought Imcu as a DPS class, but had to switch to CC and Healing. While my gear was insufficient, it didn't even show because of how bad I was at changing roles.
Also from the healer side - any healer can tell you which tanks have good HP and mitigation in the specs/gear. You guys have been doing very well at gearing up and practicing in other instances. Some people (Holly comes to mind since I just played with her the other night) are geared very well. She's been through lots of instances lots of times to get the good stuff. Other tanks have more recently hit 70 and haven't had time to hit the 5-mans as much. Not a biggie, you're getting there, keep up the good work

If you wonder where you fall, ask a healer after a run how hard you were to keep alive. While I may not know how dodge/block/def exactly works, i know they work together to give me more than 3 seconds to heal you before you die
Anyway, enough rambling. keep up the good work! I look forward to the next run.