You could use the level 70 practice dummies in the capital cities. They're great for testing castsequence and dps.

Edit: As far as I can tell, 30 seconds to kill a drake is about right. The things have 72k~ HP, and at 30 seconds, your group would be putting out 2400 DPS, which is a bit low, but only at about 80% of what my marginally well geared group does. Bottom line, I don't think there is any single contruibuting factor you can "fix" that will make your group run better. Gear wise, your paladin is good. I would suggest getting the full frostweave sets for your clothies (barring idivididual pieces that may be better) and potentially the crafted mail spell damage set (assuming it exists. Haven't looked in to that).

Are you using all your avilable DoTs and Debuffs? Those can make a big difference.

On the shadow priest: they always have low DPS compared to other DPS classes, which will pull down your group DPS, but the returned health is worth it, and I don't think you'll improve your group by switching specs on your shaman and priest, since you'll probably run in to the same problem of low dps on the Shaman. Also, watch those mind flays. Too often my priest stands there like an idiot because he hits mind flay in his castsequence and he's out of range.

You could consider having your resto shaman spam Lightning Bolt with the other DPS, just set his macros to have priority for healing. This typically doesn't work for bosses as you go OOM faster, but will pull your group DPS up a bit on trash.

Consider using an infernal or doomguard on your Lock. Infernals now have a short life span, and doomguards have 15 minute lifespan, both with a longer cool down, but both are superior DPS to even the felguard. Also, they no longer go rogue after a period of time, they just despawn, and the doom guard doesn't actually kill a party member now, he just takes a chunk of their life. Worth looking in to if the dragon stables are giving you trouble.

Binding "/castsequence Fire Elemental Totem, Heroism" is also a good short term group wide DPS boost.

I'd really suggest speccing in to Icy Veins instead of Focus Magic. In the long run in a susatined DPS situation, if your target can keep their crits going, yes, fcosu magic works out to more damage. The fact that your lock has a relatively limited crit chance, and your shadow priest shouldn't be a big crit machine period, the 20% increased damage for 20 seconds every other fight will probably work out better for you in dropping trash and 5-man bosses.

Geez, that worked out to be longer than I expected. Anyway, if you want to post your castsequences, I'll take a look at those and tell you what I think.