I'm sure there are already threads on this topic, but I'm not going to search through this whole forum to find them :P
I am a DK and I consider DW Frost my "main spec". However out of necessity, ever since dual specs came out I have always had a tank spec. Often my guild would be looking for a tank for heroics or something, and I wanted to help out. As an added bonus, it obviously keeps me from having to wait 45 minutes to get into a heroic. Herein lies my dilemma.
I was running a heroic with 3 guild mates the other day. I was tanking and we ended up pugging the last DPS, which ended up being a fury warrior. My guildies understood my situation, but felt the warrior deserved to be clued in: "I just want to give you fair warning that I will be rolling on plate DPS gear as it's my main spec. You're welcome to roll on tank drops if you would like." He agreed and we went on with the dungeon. Lo and behold, we had a boss drop some plate DPS and I rolled and won. He proceeded to curse me out, call me a ninja, and he rage quit.
I realize that there are lots of differing opinions on this topic. A lot of people subscribe to the opinion "If you want DPS gear, sit through the queue as DPS like everyone else". I understand the viewpoint, but respectfully disagree. This situation applies to all hybrid classes. What do you guys think about rolling for gear for a role you are not fulfilling at that time, but do regularly perform?