For my pally, I have a double problem with that. DPS queues are usually faster than tank queues and dps gear (haste/mastery) is usually better than the "tanking" gear. I end up queueing as dps, then on a fight by fight basis determining if there is better "tank" gear or "dps" gear available on a fight. For instance, on one fight there is a tank trinket and one hander that can drop. On another, there are haste/mastery bracers and cloak. If it's "dps" gear that I can use for prot, I can go ret and try to get it. If it's "tank" gear like the trinket and one hander, well, I had to queue dps so I can be ret on those fights that drop haste/mastery gear so now I have to dps in prot spec to try to get a roll on the gear I need.
Sucks that I have to game the system to get rolls on the gear I need. Sucks worse when I'm NOT bottom damage/dps most of the time.
Fetzie was referring to exactly what I mentioned here. Haste/mastery gear is better for prot pally than dodge/parry gear. Likewise for haste/hit or haste/expertise. That stuff is usually classified as "dps" gear, however, so if you want it for tanking, you need to be in ret spec or you don't get to roll for that piece. Just to make it difficult, the same queue may also have the boss that drops a tank trinket so you are already in as dps but now you need to be in prot spec if you want a chance to roll for that trinket, so you dps in prot spec for that fight.
"he doens't need healing, he doesn't need healing, he doesn't nee-WHAOSHIT!wtf was that man!". Please stop leaning on TDR. -Teng