Not nearly as much support
The first thing I found myself getting used to was not being coddled by the healers. That's something that tanks take for granted due to the unmistakable bond between healer and tank. A healer and tank are like two planetoids revolving together around the sun; a ranged DPS is like an asteroid flailing wildly through some vague, geosynchronous orbit.
You have undoubtedly heard the old adage, "If the tank dies, it's the healer's fault. If the healer dies, it's the tank's fault. If the melee dies, it's his own damned fault." Even as a boomkin, I stand by that assessment. That being said, it seems to be my own damned fault a lot.
Healers only have so much time to throw heals at ranged DPS, so my little boomkin has to be fast to get out of fire. And if I tax the healer too much, there are obvious problems. Rolling as ranged DPS, I have to have my health potions ready and be prepared to get my caboose to safety even faster than as a tank.
You don't decide where to move
When you're tanking the boss fight, you get to make the calls. Oh, sure, the raid leader is responsible for the raid strategy -- but as the tank, you're the one who actually moves the boss anywhere.
As the DPS, you get none of that luxury. You move in relationship with the boss (and thus the tank) and therefore have a much more limited set of options. It's relatively easy to do that, in a sense, but you still don't have the power of choice. And if you're a control freak, that will bother you.
As if that weren't enough, it can be tough to see what the heck's going on. When you run with a tank and any melee at all, combat doesn't look very clear. It looks like "seven low-polygon characters mashed together on top of a Consecrate." While a responsible DPS player uses an /assist macro, it'd still be nice to make out what's happening at ground zero.
You are being measured
Tanks and healers tend to be measured on a success-or-failure basis; it's relatively binary. Tanks sometimes like to whip out their health bar or avoidance numbers as if it means anything, but at the end of the day: pass/fail.
DPS aren't so lucky. For all that we joke about the "epeen" of DPS, and for all that I personally spend time saying Interrupt is the new damage, the world at large still cares about the size of your damage meter.
The damage meters say very clearly what your relative worth is compared to the other damage dealers. Even if you're the one interrupting, laying down CC, and maybe never taxing the healers, the damage meter still coldly spits out its metrics as if judging your life's worth.
This is a hard thing to get past. You have to discipline yourself and trust that you're doing the right thing by moving out of fire, instead of squeezing that next bit of damage. It's hard, but it must be done.
A word to other tanks
Like I said, I spend most of my time tanking. I've tanked on every class and probably always will. It's what I do -- I love tank. And when you tank, it can be very easy to get riled with the DPS.
My suggestion to other tanks is to get over it and cut them a break. While repeat offenders can be frustrating, ranged DPS is often a little more difficult than we give it credit. Work together, and we'll all be just fine.
Ready Check shares all the strategies and inside information you need to take your raiding to the next level. Be sure to look up our strategy guides to Cataclysm's 5-man instances, and for more healer-centric advice, visit Raid Rx.