First off, Kleps is a witch. True story.
Tanks die if you don't heal them. True story. This is sort of more paladin specific, because it's related to beacon of light. I've always beacon healed, even back before they made beacon healing easier, but the change to full transfer of beacon heals has currently got me to the point where I assume that any heal I cast is also going to heal my tank as well. This turns out to be a problem when either beacon has worn off, or beacon is not on the tank I'm thinking of. It happened a few nights ago on Razorscale, where I had beacon on the left side tank, so I could also spot heal and heal the sentinel tank, but then a different tank picked him up in the ground phase, and I didn't switch beacon, so the heals I thought were being sent to the main tank were in fact going to the guy who was holding the last few remaining adds, and the tank died. Fortunately, only a single ret paladin was killed before a secondary tank grabbed him, so no huge loss. It also happened last night, while fighting Anub (go go first Anub kill! whoo!), where Beacon fell off the MT right as Anub surfaced, and he had run out of range. Either of those alone wouldn't be a problem, because I can heal him if he's in range without beacon, or I can use the 60 yard beacon transfer to heal him until I get a chance to move back in range, but both together means the tank isn't getting healed, and as previously stated, tanks die if they don't get healed.
On the subject of Anub, if you stack too many healers, bosses will enrage. True story. In all our previous anub attempts, we either had the boss hit his hard enrage at about 60% if we burned the burrowers, or our offtanks died to stacking add debuffs if we tried to hold the burrowers until the submerge phase. And we tried a dozen different methods of burning one and holding three, or burning two and holding two, or leaving certain people on the boss and having everyone else burn, and we never managed to get him anywhere close to dead. We finally did figure out the right solution, which was to pull the adds to Anub's butt and AoE all three, so that anub was constantly taking damage even while the adds were up, and he still enraged. I wouldn't say our DPS is the best in the world, but we thought they at least had the output to get normal mode 25 Anub down. When we got him to 24k health before his enrage finally wiped us, with zero deaths prior to the enrage, someone finally had to say, "Do we really need seven healers for this?" So the resto druid pops over to boomkin, and we kill him with three minutes to spare. And yet, they still say, "Who's our seventh healer for farm night ulduar content?" True story.